RDSB v Chaetomorph
- Thread starter jriechel
- Start date
<a href=showthread.php?s=&postid=12111126#post12111126 target=_blank>Originally posted</a> by Randy Holmes-Farley
Growing macroalgae reduces phosphate as well as nitrate. It also exports metals. Sand beds do not. That's the huge difference and makes macroalgae a big plus over sand beds, IMO.
I actually choose to use Caulerpa racemosa, but I know that most prefer Chaetomorpha for its lack of invasiveness, despite potentially being less efficient (at least in some systems). I light mine 24/7.
I may be wrong but doesnt Caulerpa also go sexual fromt ime to time? By doing this it is alowed to spread and grown faster thourght out the tank.
I was under the impression that this was anthoer major draw back of it.
I may be wrong but doesnt Caulerpa also go sexual fromt ime to time? By doing this it is alowed to spread and grown faster thourght out the tank.
I was under the impression that this was anthoer major draw back of it.
That does seem to concern some folks. I've grown it for over a decade and that never happened, despite the fact that a small patch of a particular variant of C. racemosa (peltata) did so. I don't really think that concern is a big one for refugium use. I also do not think the concern is as much spreading via reproduction as reduced O2 as the spores die and break down, but since I've not had it happen, I cannot really comment on what concerns other folks have.
I was under the impression that this was anthoer major draw back of it.
That does seem to concern some folks. I've grown it for over a decade and that never happened, despite the fact that a small patch of a particular variant of C. racemosa (peltata) did so. I don't really think that concern is a big one for refugium use. I also do not think the concern is as much spreading via reproduction as reduced O2 as the spores die and break down, but since I've not had it happen, I cannot really comment on what concerns other folks have.
From all the responses so far, I have gained some valuable insight regarding these issues. However, I do not think that I have a solid understanding of an answer to my original question that started this thread.
Assuming that if a RDSB is setup as advertised, i.e., >9in sand with 2in of sufficiently moving water over the top of the sand to prevent any detritus buildup, dark, and supplied with post-filtered water, then nitrogen reduction to N2 will cause its removal into the atmosphere. The net effect is nitrate going to gaseous nitrogen and being removed. This is the only function of the RDSB. The rate of this removal has not been established as far a I have been able to discover.
I understand that the primary function of remote chaetomorpha culture is nitrate removal through growth and disposal. Apparently, there are other nutrients, especially phosphate, that algae in general are removing. Rates of removal seem to have uncertainty associated with this method too.
My question is ultimately based upon these unknown rates of removal, and therefore probably not fully answerable. Nevertheless, I'll try it anyway. Lush Chaetomorpha growth removes nitrates and phosphates. Is phosphate removal via this technique efficient/fast enough to warrant having it rather than a phosphate reactor? Does a RDSB remove nitrates more efficiently/faster than algae?
These questions then lead to all the "how big do I need to make..." questions, to which you will reply, "depends on gallonage, bioload, feeding regime, etc." and I'm left without any help in designing and sizing these components.
Hoping for, but not expecting, definitive answers to the above questions, how about this one; am I correct in concluding that it's all trial and error? Try what you want, see if it works, and change it if it doesn't? I don't mean to be flippant. I am honestly asking these questions. Thanks for your willingness to help.
Assuming that if a RDSB is setup as advertised, i.e., >9in sand with 2in of sufficiently moving water over the top of the sand to prevent any detritus buildup, dark, and supplied with post-filtered water, then nitrogen reduction to N2 will cause its removal into the atmosphere. The net effect is nitrate going to gaseous nitrogen and being removed. This is the only function of the RDSB. The rate of this removal has not been established as far a I have been able to discover.
I understand that the primary function of remote chaetomorpha culture is nitrate removal through growth and disposal. Apparently, there are other nutrients, especially phosphate, that algae in general are removing. Rates of removal seem to have uncertainty associated with this method too.
My question is ultimately based upon these unknown rates of removal, and therefore probably not fully answerable. Nevertheless, I'll try it anyway. Lush Chaetomorpha growth removes nitrates and phosphates. Is phosphate removal via this technique efficient/fast enough to warrant having it rather than a phosphate reactor? Does a RDSB remove nitrates more efficiently/faster than algae?
These questions then lead to all the "how big do I need to make..." questions, to which you will reply, "depends on gallonage, bioload, feeding regime, etc." and I'm left without any help in designing and sizing these components.
Hoping for, but not expecting, definitive answers to the above questions, how about this one; am I correct in concluding that it's all trial and error? Try what you want, see if it works, and change it if it doesn't? I don't mean to be flippant. I am honestly asking these questions. Thanks for your willingness to help.
Aquarist007
New member
The phosban reactor with GFO media is probally more effecient at removing phosphates from your system.
You have to have a fairly big fuge with a good amount of chaeto in it to really make a difference in nitrate and phosphate reduction.
Both systems however work much more effectively if you have taken steps to limit the importing of phosphates and nitrates in your tank prior to setting them up.
You have to have a fairly big fuge with a good amount of chaeto in it to really make a difference in nitrate and phosphate reduction.
Both systems however work much more effectively if you have taken steps to limit the importing of phosphates and nitrates in your tank prior to setting them up.
CaptainCoral
New member
Hello all.
An eye opening experience for me was a trip here a few years ago when passing through Indiana. An employee took me on a one hour tour with his girlfriend and lunch waiting. The Archemedes screw was very impressive! The wider my eyes got the more he wanted to show me. There is no denying the effectiveness of these methods in person.
I came home with a Styrofoam box of assorted goodies (including their live sand) that took up nearly the entire back seat.
To me we should be celebrating the ability to have these choices of one or another rather than pit them against each other. It they both work, shouldn't we be happy to be able to choose one method we feel comfortable with or feel would best suit our system or maintenance needs? Or the ability to use both in the same system?
An eye opening experience for me was a trip here a few years ago when passing through Indiana. An employee took me on a one hour tour with his girlfriend and lunch waiting. The Archemedes screw was very impressive! The wider my eyes got the more he wanted to show me. There is no denying the effectiveness of these methods in person.
I came home with a Styrofoam box of assorted goodies (including their live sand) that took up nearly the entire back seat.
To me we should be celebrating the ability to have these choices of one or another rather than pit them against each other. It they both work, shouldn't we be happy to be able to choose one method we feel comfortable with or feel would best suit our system or maintenance needs? Or the ability to use both in the same system?
I understand that the primary function of remote chaetomorpha culture is nitrate removal through growth and disposal. Apparently, there are other nutrients, especially phosphate, that algae in general are removing. Rates of removal seem to have uncertainty associated with this method too.
There is no significant uncertainty in the amounts of nitrogen and phosphorus taken up my macroalgae. Of course, the growth rate vary with lighting and other factors, but 1 dry pound of Chaeto will contain a relatively fixed amount of nitrogen and phosphorus that it took up to grow.
The big question is whether you are willing to devote the space and other factors needed to grow adequate macroalgae, and also perhaps in exactly how low you want and expect the macroalgae to drop the phosphate and nitrate. Folks often use less than could be used, but that is a choice, and is a fine method to combine with other methods, like GFO, sand beds, etc.
There is no significant uncertainty in the amounts of nitrogen and phosphorus taken up my macroalgae. Of course, the growth rate vary with lighting and other factors, but 1 dry pound of Chaeto will contain a relatively fixed amount of nitrogen and phosphorus that it took up to grow.
The big question is whether you are willing to devote the space and other factors needed to grow adequate macroalgae, and also perhaps in exactly how low you want and expect the macroalgae to drop the phosphate and nitrate. Folks often use less than could be used, but that is a choice, and is a fine method to combine with other methods, like GFO, sand beds, etc.
liveforphysics
New member
IMHO- I believe that macro algae is commonly applied in a mannor which makes it absolutely useless, and/or a hazard to the tank.
Algae is only working in your system while it is growing. I see people's tanks with chaeto clumps so old they have coraline spots on them... This means your chaeto is NOT doing anything, and therefore is a liability to die and cause it's biomass to disolve back into the water.
People also struggle with the idea of what rapid growth is for algea. If you increase biomass by perhaps 50% in a month, you are not doing much for your system. Yes, any algae you remove does take N
from the water, yet with slow growth rates your tissue is leaking back and forth nutrients, not doing much for pH, and mostly just being for looks. Just from general eperience, it seems about 80% of peoples tanks I see have macroalgae serving no nutrient export function.
Sucessful macroalgae growth means pulling out chunks like this on a weekly basis. This was just on a 55gal SPS tank with a 30gal fuge.
Only the rate of increase in biomass of the algae matters to the tank. Having 200lbs of static Chaeto in your fuge is only a liability for your tank.
Chaeto is a string of cells, it has no lateral growth ability. It is able to grow from each end of the string only. If you harvest your chaeto by violantly ripping out fistfulls, or by snipping with sissors, you leave many ends for new growth to occur.
Optimize your macro algae for fast growth, and harvest the old from your system. I've taken the time to straighten out an old string of chaeto before to find the string to be over 6ft before it broke. This means you have a ton of biomass of algae with only 2 end points that are capable of growth. Since growth is all that matters, this wad is not helping your tank do much at all. It's just blocking light from young short strings that could be in a rapid growth state.
Also, on topic, I dont not believe that DSBs actually have any point in which N2 evolves out of the water. N2 is kept pretty saturated by our atmosphere, and it's something that just gets cycled through different thermodynamic bio states once it enters the system. It definately works in sewer treatment applications with 1,000's of PPM N, but I've come to not believe it has any function in a low nutrient reef aquarium. Just my $0.02
Thanks for taking the time to give your input on this Randy!
Algae is only working in your system while it is growing. I see people's tanks with chaeto clumps so old they have coraline spots on them... This means your chaeto is NOT doing anything, and therefore is a liability to die and cause it's biomass to disolve back into the water.
People also struggle with the idea of what rapid growth is for algea. If you increase biomass by perhaps 50% in a month, you are not doing much for your system. Yes, any algae you remove does take N
from the water, yet with slow growth rates your tissue is leaking back and forth nutrients, not doing much for pH, and mostly just being for looks. Just from general eperience, it seems about 80% of peoples tanks I see have macroalgae serving no nutrient export function.Sucessful macroalgae growth means pulling out chunks like this on a weekly basis. This was just on a 55gal SPS tank with a 30gal fuge.
Only the rate of increase in biomass of the algae matters to the tank. Having 200lbs of static Chaeto in your fuge is only a liability for your tank.
Chaeto is a string of cells, it has no lateral growth ability. It is able to grow from each end of the string only. If you harvest your chaeto by violantly ripping out fistfulls, or by snipping with sissors, you leave many ends for new growth to occur.
Optimize your macro algae for fast growth, and harvest the old from your system. I've taken the time to straighten out an old string of chaeto before to find the string to be over 6ft before it broke. This means you have a ton of biomass of algae with only 2 end points that are capable of growth. Since growth is all that matters, this wad is not helping your tank do much at all. It's just blocking light from young short strings that could be in a rapid growth state.
Also, on topic, I dont not believe that DSBs actually have any point in which N2 evolves out of the water. N2 is kept pretty saturated by our atmosphere, and it's something that just gets cycled through different thermodynamic bio states once it enters the system. It definately works in sewer treatment applications with 1,000's of PPM N, but I've come to not believe it has any function in a low nutrient reef aquarium. Just my $0.02
Thanks for taking the time to give your input on this Randy!
I'm not sure I'd put it quite so bleakly. Dry Caulerpa racemosa has about 1/12 as much phosphate by weight as flake foods. I show that here:
Phosphate and the Reef Aquarium
http://reefkeeping.com/issues/2006-09/rhf/index.php
So if you remove ten fold as much dry mass of macroalgae as you feed in dry flake foods, then you are likely exporting plenty.
From the article:
For example, Caulerpa racemosa collected off Hawaii contains about 0.08 % phosphorus by dry weight and 5.6% nitrogen. Harvesting 10 grams (dry weight) of this macroalgae from an aquarium would be the equivalent of removing 24 mg of phosphate from the water column. That amount is the equivalent of reducing the phosphate concentration from 0.2 ppm to 0.1 ppm in a 67-gallon aquarium. All of the other species tested gave similar results (plus or minus a factor of two). Interestingly, using the same paper's nitrogen data, this would also be equivalent to reducing the nitrate content by 2.5 grams, or 10 ppm in that same 67-gallon aquarium.
Phosphate and the Reef Aquarium
http://reefkeeping.com/issues/2006-09/rhf/index.php
So if you remove ten fold as much dry mass of macroalgae as you feed in dry flake foods, then you are likely exporting plenty.
From the article:
For example, Caulerpa racemosa collected off Hawaii contains about 0.08 % phosphorus by dry weight and 5.6% nitrogen. Harvesting 10 grams (dry weight) of this macroalgae from an aquarium would be the equivalent of removing 24 mg of phosphate from the water column. That amount is the equivalent of reducing the phosphate concentration from 0.2 ppm to 0.1 ppm in a 67-gallon aquarium. All of the other species tested gave similar results (plus or minus a factor of two). Interestingly, using the same paper's nitrogen data, this would also be equivalent to reducing the nitrate content by 2.5 grams, or 10 ppm in that same 67-gallon aquarium.
This is getting at the heart of my question. I never disputed that the algal % composition for N or P had significant uncertainty (for an aquarist's purpose). It's the uncertainty in the rate of removal that strikes me as so variable as to render making a sound refugium design unlikely.
I'm not understanding something in your reply. If algae is 1/12 the phosphate of dry foods, then removing only 10x the mass of alga is a net phosphate gain in your tank. Why do you say there would be a net export? Wouldn't you need to be in excess of 12x to be in the black on phosphate export? Are you assuming that dry food wouldn't be fed exclusively and that other staples are significantly lower in phosphate?
Also, are your phosphate reduction values in a hypothetical 67g tank linearly proportional? Can I scale your values upward to the 180g tank I'm designing? Since my tank will be 2.7x as big as your 67g, is it correct to figure a 1 ppm reduction in phosphate via algae removal is equivalent to 270 grams of dry algae? If correct, what refugium volume/algae amount is needed for this amount of growth? This would be for to a rotating ball of Chaetomorhpa. Can this even be estimated?
liveforphysics
New member
If you have a static water quanity with a pre-determined nutriend concentration, then yes, it would scale fine.
However, water volume has very little to do with the rate at which you are adding nutrients. I've had 90gal tanks with a single goby and hundreds of corals, and I've had 30gal tanks with loads of fish that all got over fed.
Because the tank was 90gal does not mean it required a larger fuge than the 30gal tank. You simply must provide the means balance what you put in with what you take out.
Also, giant chaeto balls with old chaeto can be massive, yet due to the limited amount of ends to grow from vs volume, the growth is much slower than a small clump optimized for growth. The trick is to get strong water flow and strong USEFUL light to the chaeto.
Something I always find neat about a proper fuge. You can have massive amounts of HPS (algae's dream light) hitting the glass walls of a fuge, yet not even a hint of nuisance algae. Algae needs 2 things to grow. Light and food. I'm giving it all the light it can get, but the chaeto is able to keep some needed nutrient down at levels where it can't get started growing.
Could be un-related, but when I used to skim (in the conventional ways), I always had visible diatoms on the glass of the fuge. Since stopping, the glass has coraline slowly creep across it, but not diatoms. I attribute this to the increased health and growth rate of the chaeto.
I am planning to skim again, but it will be large volume large contact time recirculating cone type skimmer with only a dribble in and dribble out of tank water feeding it. I want it to be more like a steady very slow continuous water change sort of effect rather than something you try to circulate the tank volume through. On a 310gal display with 150gal of fuges/sumps, I plan to only run about 10-20gal/per day through the skimmer. I'm hoping this will not upset the growth of the algae, yet keep concentration levels of compounds which the algae may not be able to absorb lower.
Best Wishes,
-Luke
However, water volume has very little to do with the rate at which you are adding nutrients. I've had 90gal tanks with a single goby and hundreds of corals, and I've had 30gal tanks with loads of fish that all got over fed.
Because the tank was 90gal does not mean it required a larger fuge than the 30gal tank. You simply must provide the means balance what you put in with what you take out.
Also, giant chaeto balls with old chaeto can be massive, yet due to the limited amount of ends to grow from vs volume, the growth is much slower than a small clump optimized for growth. The trick is to get strong water flow and strong USEFUL light to the chaeto.
Something I always find neat about a proper fuge. You can have massive amounts of HPS (algae's dream light) hitting the glass walls of a fuge, yet not even a hint of nuisance algae. Algae needs 2 things to grow. Light and food. I'm giving it all the light it can get, but the chaeto is able to keep some needed nutrient down at levels where it can't get started growing.
Could be un-related, but when I used to skim (in the conventional ways), I always had visible diatoms on the glass of the fuge. Since stopping, the glass has coraline slowly creep across it, but not diatoms. I attribute this to the increased health and growth rate of the chaeto.
I am planning to skim again, but it will be large volume large contact time recirculating cone type skimmer with only a dribble in and dribble out of tank water feeding it. I want it to be more like a steady very slow continuous water change sort of effect rather than something you try to circulate the tank volume through. On a 310gal display with 150gal of fuges/sumps, I plan to only run about 10-20gal/per day through the skimmer. I'm hoping this will not upset the growth of the algae, yet keep concentration levels of compounds which the algae may not be able to absorb lower.
Best Wishes,
-Luke
It's the uncertainty in the rate of removal that strikes me as so variable as to render making a sound refugium design unlikely.
Unlikely or not, it has been the biggest export method in my tank for over a decade, so it clearly works fine if done correctly.
I'm not understanding something in your reply. If algae is 1/12 the phosphate of dry foods, then removing only 10x the mass of alga is a net phosphate gain in your tank. Why do you say there would be a net export? Wouldn't you need to be in excess of 12x to be in the black on phosphate export? Are you assuming that dry food wouldn't be fed exclusively and that other staples are significantly lower in phosphate?
I'm assuming that the growth of other organisms in the tank are also taking up a lot of phosphate. Fish, corals, algae, coralline algae, snails, hermit crabs, starfish, anemones, bristle worms, etc. all take up phosphate as they grow.
Also, are your phosphate reduction values in a hypothetical 67g tank linearly proportional? Can I scale your values upward to the 180g tank I'm designing? Since my tank will be 2.7x as big as your 67g, is it correct to figure a 1 ppm reduction in phosphate via algae removal is equivalent to 270 grams of dry algae? If correct, what refugium volume/algae amount is needed for this amount of growth? This would be for to a rotating ball of Chaetomorhpa. Can this even be estimated?
The example I gave was a simple mathematical calculation, so it can be scaled up or down in algae mass and tank water volume as you thing suits your needs. I also agree with Luke that the balance ultimately depends on what is fed, not the water volume.
Unlikely or not, it has been the biggest export method in my tank for over a decade, so it clearly works fine if done correctly.
I'm not understanding something in your reply. If algae is 1/12 the phosphate of dry foods, then removing only 10x the mass of alga is a net phosphate gain in your tank. Why do you say there would be a net export? Wouldn't you need to be in excess of 12x to be in the black on phosphate export? Are you assuming that dry food wouldn't be fed exclusively and that other staples are significantly lower in phosphate?
I'm assuming that the growth of other organisms in the tank are also taking up a lot of phosphate. Fish, corals, algae, coralline algae, snails, hermit crabs, starfish, anemones, bristle worms, etc. all take up phosphate as they grow.
Also, are your phosphate reduction values in a hypothetical 67g tank linearly proportional? Can I scale your values upward to the 180g tank I'm designing? Since my tank will be 2.7x as big as your 67g, is it correct to figure a 1 ppm reduction in phosphate via algae removal is equivalent to 270 grams of dry algae? If correct, what refugium volume/algae amount is needed for this amount of growth? This would be for to a rotating ball of Chaetomorhpa. Can this even be estimated?
The example I gave was a simple mathematical calculation, so it can be scaled up or down in algae mass and tank water volume as you thing suits your needs. I also agree with Luke that the balance ultimately depends on what is fed, not the water volume.
Aquarist007
New member
I'm sure you have written an article on setting up a refugium the correct way as to maximize the export of nitrates and phosphates, an article I have missed and would love to read.
Could you post the link to that article Randy, I have been really focusing the increasing of my knowledge towards effective refugiums and your ideas would be a great asset.
Thanks
Scott
When discussing phosphates in a system shouldn't kalk be considered as well? How much impact does kalk have on phosphates?
I really don't think it has all that much, but whether it specifically does or not, deposition of phosphate into calcium carbonate (both abiotic and biological skeleton deposition) is an important sink for phosphate, IMO.
I discuss the limewater effect here:
Phosphate and the Reef Aquarium
http://reefkeeping.com/issues/2006-09/rhf/index.php
from it:
http://reefkeeping.com/issues/2006-09/rhf/index.php#10
Phosphate Reduction via Calcium Phosphate Precipitation
--------------------------------------------------------------------------------
One mechanism for phosphate reduction in reef aquaria may simply be the precipitation of calcium phosphate, Ca3(PO4)2. The water in many reef aquaria is supersaturated with respect to this material, as its equilibrium saturation concentration in normal seawater is only 0.002 ppm phosphate. As with CaCO3, the precipitation of Ca3(PO4)2 in seawater may be limited more by kinetic factors than by equilibrium factors, so it is impossible to say how much will precipitate under reef aquarium conditions (without, of course, somehow determining it experimentally). This precipitation may be especially likely where calcium and high pH additives (such as limewater) enter the aquarium water. The locally high pH converts much of the HPO4-- to PO4---. Combined with the locally high calcium level (also from the limewater), the locally high PO4--- level may push the supersaturation of Ca3(PO4)2 to unstable levels, causing precipitation. If these calcium phosphate crystals are formed in the water column (e.g., if they form at the local area where limewater hits the aquarium water), then they may become coated with organics and be skimmed out of the aquarium.
Many reefkeepers accept the concept that adding limewater reduces phosphate levels. This may be true, but the mechanism remains to be demonstrated. Craig Bingman has done a variety of experiments related to this hypothesis, and has published them in the old Aquarium Frontiers magazine. While many aquarists may not care what the mechanism is, knowing how it occurs will help us understand the limits of this method, and how to best employ it.
One possible mechanism could be through calcium phosphate precipitation, as outlined above. A second mechanism for potential phosphate reduction when using high pH additives is the binding of phosphate to calcium carbonate surfaces. The absorption of phosphate from seawater onto aragonite is pH dependent, with the binding maximized at around pH 8.4 and with less binding occurring at lower and higher pH values. Habib Sekha (owner of Salifert) has pointed out that limewater additions may lead to substantial precipitation of calcium carbonate in reef aquaria. This idea makes perfect sense. After all, it is certainly not the case that large numbers of reef aquaria exactly balance calcification needs by replacing all evaporated water with saturated limewater. And yet, many aquarists find that calcium and alkalinity levels are stable over long time periods with just that scenario. One way this can be true is if the excess calcium and alkalinity, which such additions typically add to the aquarium, are subsequently removed by precipitation of calcium carbonate (such as on heaters, pumps, sand, live rock, etc.). It is this ongoing precipitation of calcium carbonate, then, that may reduce the phosphate levels; phosphate binds to these growing surfaces and becomes part of the solid precipitate.
If the calcium carbonate crystal is static (not growing), then this process is reversible, and the aragonite can act as a reservoir for phosphate. This reservoir can inhibit the complete removal of excess phosphate from a reef aquarium that has experienced very high phosphate levels, and may permit algae to continue to thrive despite all external phosphate sources having been cut off. In such extreme cases, removal of the substrate may even be required.
If the calcium carbonate deposits are growing, then phosphate may become buried in the growing crystal, which can act as a sink for phosphate, at least until that CaCO3 is somehow dissolved. Additionally, if these crystals are in the water column (e.g., if they form at the local area where limewater hits the aquarium water), then they may become coated with organics and be skimmed out of the aquarium.
If phosphate binds to calcium carbonate surfaces to a significant extent in reef aquaria, then this mechanism may be attained with other high pH additive systems (such as some of the two-part additives, including Recipe #1 of my DIY system). However, this potential precipitation of phosphate on growing calcium carbonate surfaces will not be as readily attained with low pH systems, such as those using calcium carbonate/carbon dioxide reactors or those where the pH is low due to excessive atmospheric carbon dioxide, because the low pH inhibits the precipitation of excess calcium and alkalinity as calcium carbonate, as well as inhibiting the binding of phosphate to calcium carbonate.
I really don't think it has all that much, but whether it specifically does or not, deposition of phosphate into calcium carbonate (both abiotic and biological skeleton deposition) is an important sink for phosphate, IMO.
I discuss the limewater effect here:
Phosphate and the Reef Aquarium
http://reefkeeping.com/issues/2006-09/rhf/index.php
from it:
http://reefkeeping.com/issues/2006-09/rhf/index.php#10
Phosphate Reduction via Calcium Phosphate Precipitation
--------------------------------------------------------------------------------
One mechanism for phosphate reduction in reef aquaria may simply be the precipitation of calcium phosphate, Ca3(PO4)2. The water in many reef aquaria is supersaturated with respect to this material, as its equilibrium saturation concentration in normal seawater is only 0.002 ppm phosphate. As with CaCO3, the precipitation of Ca3(PO4)2 in seawater may be limited more by kinetic factors than by equilibrium factors, so it is impossible to say how much will precipitate under reef aquarium conditions (without, of course, somehow determining it experimentally). This precipitation may be especially likely where calcium and high pH additives (such as limewater) enter the aquarium water. The locally high pH converts much of the HPO4-- to PO4---. Combined with the locally high calcium level (also from the limewater), the locally high PO4--- level may push the supersaturation of Ca3(PO4)2 to unstable levels, causing precipitation. If these calcium phosphate crystals are formed in the water column (e.g., if they form at the local area where limewater hits the aquarium water), then they may become coated with organics and be skimmed out of the aquarium.
Many reefkeepers accept the concept that adding limewater reduces phosphate levels. This may be true, but the mechanism remains to be demonstrated. Craig Bingman has done a variety of experiments related to this hypothesis, and has published them in the old Aquarium Frontiers magazine. While many aquarists may not care what the mechanism is, knowing how it occurs will help us understand the limits of this method, and how to best employ it.
One possible mechanism could be through calcium phosphate precipitation, as outlined above. A second mechanism for potential phosphate reduction when using high pH additives is the binding of phosphate to calcium carbonate surfaces. The absorption of phosphate from seawater onto aragonite is pH dependent, with the binding maximized at around pH 8.4 and with less binding occurring at lower and higher pH values. Habib Sekha (owner of Salifert) has pointed out that limewater additions may lead to substantial precipitation of calcium carbonate in reef aquaria. This idea makes perfect sense. After all, it is certainly not the case that large numbers of reef aquaria exactly balance calcification needs by replacing all evaporated water with saturated limewater. And yet, many aquarists find that calcium and alkalinity levels are stable over long time periods with just that scenario. One way this can be true is if the excess calcium and alkalinity, which such additions typically add to the aquarium, are subsequently removed by precipitation of calcium carbonate (such as on heaters, pumps, sand, live rock, etc.). It is this ongoing precipitation of calcium carbonate, then, that may reduce the phosphate levels; phosphate binds to these growing surfaces and becomes part of the solid precipitate.
If the calcium carbonate crystal is static (not growing), then this process is reversible, and the aragonite can act as a reservoir for phosphate. This reservoir can inhibit the complete removal of excess phosphate from a reef aquarium that has experienced very high phosphate levels, and may permit algae to continue to thrive despite all external phosphate sources having been cut off. In such extreme cases, removal of the substrate may even be required.
If the calcium carbonate deposits are growing, then phosphate may become buried in the growing crystal, which can act as a sink for phosphate, at least until that CaCO3 is somehow dissolved. Additionally, if these crystals are in the water column (e.g., if they form at the local area where limewater hits the aquarium water), then they may become coated with organics and be skimmed out of the aquarium.
If phosphate binds to calcium carbonate surfaces to a significant extent in reef aquaria, then this mechanism may be attained with other high pH additive systems (such as some of the two-part additives, including Recipe #1 of my DIY system). However, this potential precipitation of phosphate on growing calcium carbonate surfaces will not be as readily attained with low pH systems, such as those using calcium carbonate/carbon dioxide reactors or those where the pH is low due to excessive atmospheric carbon dioxide, because the low pH inhibits the precipitation of excess calcium and alkalinity as calcium carbonate, as well as inhibiting the binding of phosphate to calcium carbonate.
I'm sure you have written an article on setting up a refugium the correct way
Actually, I haven't. Might be a good idea for the future, however.
Actually, I haven't. Might be a good idea for the future, however.
<a href=showthread.php?s=&postid=12259623#post12259623 target=_blank>Originally posted</a> by Randy Holmes-Farley
Unlikely or not, it has been the biggest export method in my tank for over a decade, so it clearly works fine if done correctly.
This is very encouraging news. I was unaware that algae scrubbing was your main export method. I would be very interested in how to do it correctly. Will you share your setup, such as tank/fuge sizes, lighting, flow rates, "harvesting" rates, and bioload? Of course, any other vital parameter you have come to recognize as necessary for success would be very welcome.
Regarding bioload, your, and Luke's, point referencing this parameter's significance over simple gallons makes perfect sense. I'm a little embarassed that I didn't think of it. Has anyone quantified bioload? A 5 inch grouper would seem to contribute more to bioload than 5 one-inch damsels, yet all the rules that I've read only mention total inches of fish. How about a total inch/girth ratio?
Aquarist007
New member
I'll second that request and so would alot of reefers on this site
http://www.reefcentral.com/forums/showthread.php?s=&threadid=1349443
http://www.reefcentral.com/forums/showthread.php?s=&threadid=1349443
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