Dsb's work, what makes them work best?
- Thread starter barryhc
- Start date
Lobster
Premium Member
Ok, I've been reading this thread and have a point to make.
PO4 is imported from any number of sources, including feeding fish, adding phyto to the tank, etc. You will have phosphate coming in to a reef tank in some amount. It's mostly unavoidable.
Now, algae needs light and phosphate, as we all know. To get rid of algae in a lighted tank, you must reduce available phosphate in the system. This means having a means of constantly exporting phosphate from the system, and keeping the level low. You must avoid recycling phosphate back into the water. Algae is merely a temporary vessel for the phosphate - it is not the sickness, it is the symptom. Therefore, buying a fish to eat algae and poop phosphate back into the system is not a solution. It's like using a cow to stop grass from growing. Similarly, using macroalgae to "tie up" phosphate is not a strong solution without heavy macro export (but is still a wild card, IMO).
Consider the reverse scenario - remove the light from the system. Obviously, the algae dies, but phosphate in the dying algae returns to the system. We also know phosphate is stored in rock in some form, since "cooking" rock causes a rock to shed detritus, which presumably contains some PO4. Without removing the phosphate from either of the above sources, turning the light back on cranks up algae growth again.
We all agree at this point that both DSB and BB can succeed given they are run properly. We know DSB and BB can handle breaking down ammonia and all that - I think the most common problem is phosphate. That said, I know how a BB system deals with phosphate. The system is initially setup to be "phosphate-starved" and detritus is kept in suspension and wet-skimmed away, or removed via water changes and direct removal (vaccuuming).
My big question about DSB's is simple: what is the "right way" to ensure that phosphate is constantly exported? In a BB tank, detritus is ideally removed by removing detritus before it breaks down and releases bound phosphate. A BB tank should not allow detritus to sit idle anywhere - no pile of rocks in the sump, no sandy refugium, no sponges, no filter sock... no detritus! In a DSB, detritus does sit idle and decays, by design, releasing phosphate into the water. What is the phosphate-export function in a DSB? Whether detritus decays on top of the sandbed, or in the sandbed, I can't figure out how I'm supposed to get phosphate out of the water before the algae beats me to it.
Can someone point me to some reference explaining this part?
Over the past decade, I've heard volumes of bad advise. I've done things "the wrong way" with both BB and DSB, and I know they both can fail, but phosphate problems are the one part of a DSB that keeps the sand out of my tank.
The process of nitrification/denitrification is constantly releasing low levels of phosphorus. You can't do anything about it. If you don't have a sandbed, the majority of this is going to come from your rocks.
In a plenum ala Sprung/Goemans, you are supposed to frequently vacuum out solids so that as few as possible solids dissolve. You have a screen that separates the aerobic zone from the lower zones so you won't won't disturb them by vacuuming. You are also supposed to have enough flow that as few as possible solids land on the bed. You will still have the low level phosphorus release that occurs during nitrification/denitrification.
In a DSB, you don't vacuum. You are supposed to house a lot of critters to break the solids down as much as possible and then store the phosphorus. You are supposed to let cyanobacteria and algaes get the phosphates. What the algaes don't get will be picked up by your skimmer. If you abuse (too much bioload/too little flow/etc.) your DSB over years and years, detrital mulm will start filling it up. In other words, your anaerobic layer will keep getting thicker, your aerobic will keep getting thinner, and eventually you'll get the "burp" of large levels of phosphorus as opposed to the low level release that is from nitrification/denitrification.
Sure it is, it's called the "eat-poop-skim" method.
Actually, it's more like birds eating the grass, and the skimmer is catching the poop in "mid flight".
Quite correct, Chaeto seems to be the big winner here.
I agree, the same goes for DSB.
There is no single right way, there are many. There is no "magic bullet". In this respect, the BB "instructions" are "simpler" than for DSB.
This simply isn't true. It may be true of "ONE DESIGN", but that is not the ONLY design.
High flow, detrivores, and skimming, same as BB.
And many others as well. This is what we're working on here. Discussion of the processes that occur, at, and most especially below, the Hypoxic "Nitrate Reducing Zone" are especially important, as this is where Phosphate "binding and leaching", "Hydrogen Sulfide production", and "Heavy Metals Sinking" occurs. ( or not, if you insist )
and back to The "rest of the story" !
> barryhc
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Lobster
Premium Member
My understanding is that if you minimize decay in the tank, you minimize fuel for denitrification. A DSB promotes nitrification/decay, no?
So having algae problems is normal in a DSB? How does the skimmer remove the phosphate the algae and bacteria miss? I don't think you can skim phosphate. Sorry I have so many questions.
Ok, well what are some of the many right ways to export phosphate. You said "skim fish poop" method, so I assume you mean fish/snails eat algae and you skim the waste, but how do you stop waste from decaying on the sand when you cannot clean the sandbed? I tried this method and had the same experience as Joe's tank. The bed ran fine until one day I had turf algae problems. Never could tell what I did wrong, as I thought I followed the directions. I guess I was too stupid to figure it out. Bummer too... sand is so pretty.
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Sindjin
New member
This is a terrific thread. So much great info .
I just wanted to chime in and once again emphasize the importance of Cooking your Rock completely before placing it on top of a new sandbed. To me, this is the MOST important thing you could do. Because then you KNOW that no detritus/PO4 will be shed from the rock and settling into the sandbed. It would put YOU in control of your closed system that much more.
I just wanted to chime in and once again emphasize the importance of Cooking your Rock completely before placing it on top of a new sandbed. To me, this is the MOST important thing you could do. Because then you KNOW that no detritus/PO4 will be shed from the rock and settling into the sandbed. It would put YOU in control of your closed system that much more.
npaden
New member
Okay, after watching for the last dozen pages or so I guess I'll jump back in here with a couple comments now that we seem to be getting trolled a little.
Lobster, there were several ways mentioned to export phosphate. Skimming and macroalgae export are the most effective. One thing I'm finding out is that you can sell cheato that you remove from your refugium for a lot more than you can sell snail poop that you've siphoned from your BB tank. One thing I've always wondered about BB tanks is that if there is no phosphate and no algae, why do you even need snails and what are the snails eating that makes them need to poop?
One constant that we are seeing in any well run system is good flow, good skimming and a good export system. On a DSB tank the export is typically macro algae, in a BB tank it is siphoning the bottom.
Let's try to keep this on target on effective methods to run a DSB tank and not get into a debate here.
FWIW, Nathan
Lobster, there were several ways mentioned to export phosphate. Skimming and macroalgae export are the most effective. One thing I'm finding out is that you can sell cheato that you remove from your refugium for a lot more than you can sell snail poop that you've siphoned from your BB tank. One thing I've always wondered about BB tanks is that if there is no phosphate and no algae, why do you even need snails and what are the snails eating that makes them need to poop?
One constant that we are seeing in any well run system is good flow, good skimming and a good export system. On a DSB tank the export is typically macro algae, in a BB tank it is siphoning the bottom.
Let's try to keep this on target on effective methods to run a DSB tank and not get into a debate here.
FWIW, Nathan
Correct. My recipe for ANY tank is sufficient flow to remove waste via a skimmer. I don't care if it's SSB, BB, DSB, Plenum, CC, etc. You want to remove as much waste as possible. However, even if you could remove 100% of fish and coral poop instantly, you will still need nitrifcation and denitrification. Fish are constantly releasing Ammonia from their gills. The bacteria solve this problem for you.
So having algae problems is normal in a DSB? How does the skimmer remove the phosphate the algae and bacteria miss? I don't think you can skim phosphate. Sorry I have so many questions.
First off, don't be sorry for questions. It's how all of us learn. People will learn from your questions and I learn from reading other peoples questions.
Algae problems is really a matter of degree. There are tons of microalgaes that you barely see and cyanobacteria is always present in your tank....you just might not see them.
You are correct, you cannot skim phosphates directly but you can get them indirectly in a myriad of ways. It can bind with Calcium or Magnesium (i.e. Calcium-phosphate or Magnesium-phosphate) and then get coated with organics which will then be skimmable. Even though most bacteria reside in biofilms on/in surfaces, there are motile bacteria that run around in the water column. They hop on any available phosphorus like white on rice. These bacteria will be skimmable. There's other ways but I thought you might like this article by Randy Holmes-Farley. http://web.archive.org/web/20010309054900/http://home.mweb.co.za/jv/jv79/reef/skimmers2.html
There is no single right way, there are many. There is no "magic bullet". In this respect, the BB "instructions" are "simpler" than for DSB.
Ok, well what are some of the many right ways to export phosphate. You said "skim fish poop" method, so I assume you mean fish/snails eat algae and you skim the waste, but how do you stop waste from decaying on the sand when you cannot clean the sandbed? I tried this method and had the same experience as Joe's tank. The bed ran fine until one day I had turf algae problems. Never could tell what I did wrong, as I thought I followed the directions. I guess I was too stupid to figure it out. Bummer too... sand is so pretty.
Maximizing flow over your sandbed via a spraybar is quite useful in this regard. The sand stays put, the poop floats off. Here's one area where I'm going to agree with a popular DSB promoter (Barry, record the date and time
). If you don't have sufficient flow, have a good clean up crew inside your sandbed will be useful to move the phosphates down into the bed rather than having the reactions occur on the surface.
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I'm not so sure yet about the rock "cooking". I understand the process very well, and I may use it someday as one of the many tools that I have available.
I have a lot of tools available, including a Bare Bottom tank.
However, this thread is intended to promote the improvement of sand beds, and it will accomplish that I assure you.
Firstly, a Reef Aquarium IS NOT A CLOSED SYSTEM !
Food, Skimmer, Vacuum, Reactors, Import, Export. Give me a break ! ! ! ! Please ? ? ?
> barryhc
There will always be algae in any saltwater system. You can't avoid it....it's all a matter of degree and whether it's visible or not. Think about it. You are throwing Ammonium, nitrates, phosphates, and light, and water together in one place. The first three items I mentioned in the previous system are what farmers use to fertilize their farms.....the only difference is that farmers use the sun for the light source and rain for the water source.
<a href=showthread.php?s=&postid=6529147#post6529147 target=_blank>Originally posted</a> by inwall75
I'm going to agree with a popular DSB promoter (Barry, record the date and time
I already "let the cat out of the bag", Curt. Now it's pi$$ing on the carpet ! !
:lol: Barryhc
( duly noted, no "paper" though ! )
Sindjin
New member
Exactly. And one way to improve the quality of running a DSB is by doing as much as you can INITIALLY to be in control of the detritus that ends up in the bed. Just the other day, in another thread I was talking to someone who ordered live rock, cycled it in a seperate container for 2 weeks and placed in their display when they saw the Nitrites come down. It was way too soon and now they have tons of debris on/in the bed. IMO, it was unneccessary and could have been avoided if more people understood the benefits of Properly Curing/Cooking their rock.
In addition, like I said in the beginning of this now enormous thread... the issues of detritus, waiste import/export, husbandry, PO4, NO4....are not indicitive of just one type of system. These topics need to be understood by the REEFER. Not by the DSB'er or the BB'er.
Even though I have a BB, I have learned a ton from this thread. Not just about DSB's but the common processes that occur in the DSB and Live Rock, combined.
Thanks Sindjin, well put ! Part of my last reply was really meant for Lobster, or in general, Sorry !
On the rock cooking issue, I don't necessarily have any issues with rock cooking in general. However, my concern with detritus, is with the "ORGANIC" kind. I'm just not too worried about "MINERAL" forms of "detritus", while I have to simeltaneously put up with people telling me that my sand bed is in a "kill zone", if I don't include "flour sized" particles.
I measured the "flour", by the way, and the size is approx. .035mm, which is about half the size stated for the "minimum particle size" in "Shimek's formula".
"Bertoni" ? ? ?
Barry
On the rock cooking issue, I don't necessarily have any issues with rock cooking in general. However, my concern with detritus, is with the "ORGANIC" kind. I'm just not too worried about "MINERAL" forms of "detritus", while I have to simeltaneously put up with people telling me that my sand bed is in a "kill zone", if I don't include "flour sized" particles.
I measured the "flour", by the way, and the size is approx. .035mm, which is about half the size stated for the "minimum particle size" in "Shimek's formula".
"Bertoni" ? ? ?
Barry
Sindjin
New member
The mineral forms of detritus coming from inside the rock will have PO4 bonded to them, correct? If so, If it does enter the sandbed and sink into the "Kill Zone"...lol....sorry had to throw that in there.... wont the lower pH values in the sandbed cause that bond with the Calcerous minerals to break?
As far as the sand size .... you got me. I wasnt really following that part of the discussion with much detail.Sorry.
Well, actually, I don't really know. If they do, then is there any reason why the PO4 content is higher in the mineral portion of detritus, than it is in Araganite sand, or more interestingly, in Silica sand?
Even if there is a higher concentration of PO4 in the "mineral detritus", isn't that still bacteria food, just the same?
I believe that is true.
Come on Sindjin, "get with the program" ! :lol:
This is where the ACTION IS ! It is the beginning of the "Rest OF The Story" ! !
Barry
Look at it this way, if the PO4 is "going back into solution", and if DSB's "sink" various compounds, "deeper into the sand bed", then how can we take this condition, which appears to be an "eventual" diasadvantage, and "turn it into an advantage? ?
Plenum Wasting is one "potential" answer. H-m-m-m-m . . . .
> Barry
Plenum Wasting is one "potential" answer. H-m-m-m-m . . . .
> Barry
