Are Deep Sand Beds, DSBs, dangerous to use in a marine aquarium?

[Reefin' Dude]

trueperc- it is significantly harder to purge a substrate of phosphates. the finer the substrate the harder. unlike LR it can not effectively self clean itself. with good flow all around LR and if it is not touching a substrate LR will purge itself (cooking). a coarse substrate that is heavily siphoned clean on a regular basis theoretically is purging itself of phosphates, but it needs to be aggressively cleaned regularly in order to push the advantage of the calcium carbonate/bacteria give and take towards the bacteria instead of the calcium carbonate. in a healthy substrate there is a slow migration of phosphates downward.

wayne in normway- seagrasses, yes, but algae no. that is a very important distinction. seagrasses have true roots, algae does not. holdfasts lack the nutrient transport mechanism that roots have. over the years with keeping substrated tanks and reading the boards it seems that the length of time that it takes for a calcium carbonate based substrate to reach its maximum phosphate absorption ability is 1 year for every inch of substrate depth. there of course is a lot of variability based on the amount of feeding , the amount of available surface area of the substrate, and the amount of actual detrital removal done by the aquarist.

G~

 

[jda]

Even if you got all of the debris out of the substrate, there would still be phosphate bonded at a molecular level to the aragonite that would not come off. This bond is what needs replaced and cannot be rinsed off. However, I do think that removing the broken down organics and sludge can really help too.

I replace one bag of sand a year at about $30. I can't jack around with too many other things for that kind of money.

 

[Reefin' Dude]

what you say is true, but if you remove the detritus from between the grains you push the balance of power towards the bacteria. phosphates are going to bind to calcium carbonate, but if the bacteria are not choked out by a lack of resources (abundance of detritus can limit necessary resources for the bacteria) they will be glad to remove the phosphates from the calcium carbonate matrix. thus creating more bacterial flock (detritus).

it all boils down to how much effort one wants to put towards keeping the detritus out of a substrate as opposed to just replacing it.

G~

 

[Paul B]

I don't know if it matters but in going with this discussion, my dolomite gravel has been in my tank over my reverse UG filter for about 45 years. I have no reactors. The gravel was never removed. My phosphate is 0.2. Yes it is a little high, I have no algae but I feel that is low if it was true that phosphate is binding with my substrait.
I am certainly not an expert on phosphate but I thought I would add that just for the thread.

 

[ddiomede]

Some people are strongly for DSB's, while others are vehemently against them.

If you leave them alone and don't disturb them, you are fine. If however you add a critter that enjoys tunneling, like a pistol shrimp or jawfish, you will have problems.

But more or less, they are considered by most to be ticking time bombs.

You see many people gravitating towards having a bare bottom tank, but me personally, I don't like the look. I usually go for a very thin layer of sand, then add some clean up crew like nassarious snails that like to burrow in roughly an inch.

 

[Reefin' Dude]

it doesn't matter whether the tank is BB, DSB, or SSB. the only thing that matters is that the toilet is flushed on a regular basis.

it all boils down to how long you want to keep poo as a pet.

G~

 

[Nano sapiens]

Variable rates of phosphate uptake by shallow marine . carbonate sediments:
Mechanisms and ecological significance

more information about the uptake of phosphates by calcium carbonate in marine sediments. it is what calcium carbonate does, absorb phosphates. the important part is to know what to do with this knowledge. calcium carbonate substrates are phosphate sinks.

G~

Great find with this publication. I've been looking for something like this for quite a while.

 

[jda]

what you say is true, but if you remove the detritus from between the grains you push the balance of power towards the bacteria. phosphates are going to bind to calcium carbonate, but if the bacteria are not choked out by a lack of resources (abundance of detritus can limit necessary resources for the bacteria) they will be glad to remove the phosphates from the calcium carbonate matrix. thus creating more bacterial flock (detritus).

it all boils down to how much effort one wants to put towards keeping the detritus out of a substrate as opposed to just replacing it.

G~

I totally agree, but if I understand this correctly, even if you keep the substrate really clean, the aragonite will eventually be all bonded up, right?

Anyway, a quick vacuum on the top and sand replacement works really well for me. It works even better since I went with a wavebox and don't blow it all around anymore.

 

[Nano sapiens]

If detritrus is regularly removed bacteria can function efficiently. Bacteria liberate phosphate from the calcareous substrate, so in a balanced system there is a constant binding and release of phosphate. This released phosphate is immediately utilized by organisms in the tank for metabolism and growth. Problems occur when detritus clogs the substrate causing chemical (phosphate overload) and physical (bacteria can't function efficiently) issues. The result is an excess of phosphate in the water column which algae will happily utilize.

 

[wayne in norway]

Reefin Dude - I was rather under the impression that the holdfast systems on Caulerpa did allow for nutrient uptake, which is unusual I agree for algae. I have needed to confirm this in the past, but believe it to be the case. They can certainly absorb ammonium, nitrate out of substrates, so I would assume phosphate as well.

Ddiomede - they are indeed 'considered ticking time bombs' by many, but the point is whether that is true or not? Phosphate levels in a substrate will rise a bit, but do they continue to rise, or do they flatten off at an equilibrium. Sounds like Pauls have flatteened off, and that's also what other work actually measuring the levels have suggested.

The proviso of course is that the thing must be setup correctly.

 

[billsreef]

it doesn't matter whether the tank is BB, DSB, or SSB. the only thing that matters is that the toilet is flushed on a regular basis.

it all boils down to how long you want to keep poo as a pet.

G~

[top] This. Every method out there is a ticking time bomb without some degree of maintenance. For a DSB that would include periodic vacuuming of small sections of the sand bed, and occasionally replacing small sections, as well as critters that provide some bioturbation...stirring of the bed.

 

[Reefin' Dude]

Reefin Dude - I was rather under the impression that the holdfast systems on Caulerpa did allow for nutrient uptake, which is unusual I agree for algae. I have needed to confirm this in the past, but believe it to be the case. They can certainly absorb ammonium, nitrate out of substrates, so I would assume phosphate as well.

i believe you are talking about this article:

Uptake of sediment ammonium and translocation in a marine green macroalga Caulerpa cupressoidesl


it does not mention phosphates, but you would think that there would be some uptake through the holdfasts if ammonia is also able to be taken in. it does seem to be very little though. i am curious to find out where the ability of nutrient transport in holdfasts begins to occur. this could explain why Caulerpa seems to be able to hand on in ULNS than other forms of algae if it is able to transport some nutrients through its holdfasts. regardless of how little it can, it is still some and if there are any small pockets of detrital collection in LR that flow can not wash away, the Caulerpa could be utilizing this. if the Caulerpa in these situations is unable to grow in its normal crazy rate, this would support this thinking. the transport of nutrients is very limited in distance through the holdfasts.

Ddiomede - they are indeed 'considered ticking time bombs' by many, but the point is whether that is true or not? Phosphate levels in a substrate will rise a bit, but do they continue to rise, or do they flatten off at an equilibrium. Sounds like Pauls have flatteened off, and that's also what other work actually measuring the levels have suggested.

The proviso of course is that the thing must be setup correctly.

Paul (correct me if i am wrong) does major cleanings on regular intervals. if i remember correctly every 10 or so years. he also creates hurricanes in his system on a semi regular basis to stir things up and get the detritus out. he does export nutrients fairly regularly. the tank is not set and forget, which seems to what most aquarist think when they talk about SW systems.

G~

 

[Paul B]

i believe you are talking about this article:

[URL="http://wap.aslo.org/lo/toc/vol_29/issue_2/0374.pdf


Paul (correct me if i am wrong) does major cleanings on regular intervals. if i remember correctly every 10 or so years. he also creates hurricanes in his system on a semi regular basis to stir things up and get the detritus out. he does export nutrients fairly regularly. the tank is not set and forget, which seems to what most aquarist think when they talk about SW systems.

G~

That is correct, I do stir things up occasionally, but I doubt that by- yearly stirring would remove so many years of phosphates. But as I said, I am not a phosphate expert.
No good system will function forever with no maintenance. 5 or 6 years is not very long in the life of a reef tank

 

[Timber77]

I think the folks saying not to have sand sifters with a dsb are a little out of touch. I have had my dsb for 20+ years and have some huge engineer gobies that stir it up and a bank of wp40's no black areas and certainly its been going long enough if the theoretical phosphate bomb were to hit it would have by now... Anyone who thinks just one aspect of the hobby will make or break it a setup is fooling themselves, good husbandry skills will prevail.. I think having oversized skimmer and high flow are the keys to bb or dsb or shallow sand bed... sometimes my fish or pumps move alot of sand around, if stirring it up causes such problems I think i would have ditched the dsb along time ago... I also use silica based cheap sand from home depot and have for years, every few year i throw another bag or 2 in, to replace what gets taken out by filters, carbon and aggressive skimming.

 

[heller792]

I think the folks saying not to have sand sifters with a dsb are a little out of touch. I have had my dsb for 20+ years and have some huge engineer gobies that stir it up and a bank of wp40's no black areas and certainly its been going long enough if the theoretical phosphate bomb were to hit it would have by now... Anyone who thinks just one aspect of the hobby will make or break it a setup is fooling themselves, good husbandry skills will prevail.. I think having oversized skimmer and high flow are the keys to bb or dsb or shallow sand bed... sometimes my fish or pumps move alot of sand around, if stirring it up causes such problems I think i would have ditched the dsb along time ago... I also use silica based cheap sand from home depot and have for years, every few year i throw another bag or 2 in, to replace what gets taken out by filters, carbon and aggressive skimming.

same here, my dsb has always been the base block to any of my aquariums. My current display dsb is 5ft by 2.5ft and all rock work is lifted above the sand on pillars. My clean up crew consist of 6 conches and a pistol shrimp who tunnels all over the dsb. I also have 5 wrasses that sleep in the sand bed.

Dave

 

[brad]

I started this hobby 12 years ago, and can honestly say I never had a tank as nice as the first few years when I used a DSB. I removed it because I went through a lot of tank moves (you lose sand each time), I wanted more space in the tank (at that time a 24" tank with 4" sand), and wanted to try something else. I do like having tons of flow which prevents adding sand again, but I might do it in a refugium.

I've been hearing about SO2 being a problem almost for 12 years. In those years, I believe it has always been a theoretical problem, with no one actually reporting dead fish and fart smelling homes. I believe the theoretical problem is the equation SO2 + H20 + O2 = H2SO4 which can strip Oxygen rapidly from water. I believe fear of this is nonsense, a ton of SO2 released at once would kill your tank, but released gradually at the rate if forms, there isn't nearly enough to lower oxygen levels. Don't forget, SO2 only forms where there is no oxygen to begin with, and slowly works its way out by diffusion as oxygen slowly works its way in. There is an equilibrium between SO2 diffusing out and O2 diffusing in, with enough distance being required to form SO2 in the first place.

It seems to me there are 2 very different approaches to DSB. 1 goal is to keep the sand clean, so no nutrients accumulate, and the other is to keep the sand dirty, so nutrients feed micro-organisms or are freed as nitrogen gas. I was in the "keep the sand dirty" approach, and I've never had "sand sifters". This worked very well for periods as long as 18 months. Would it have worked longer? I don't know. I think people run into problem when they switch from 1 to the other - keep a "dirty" sand bed for years and suddenly stir everything up.

Having more experience, my main worry would be Phosphate. Denitrifying bacteria turn nitrate into nitrogen gas, but what happens to Phosphate? I don't know where it would accumulate, but it would have to unless it somehow left the system. Water changes seem like a poor way of removing phosphate.

 

[Reefin' Dude]

having been in the hobby since 91 and have tried every type of substrate and configuration at least twice. i think that the SO2 problem is a red herring. the real problem being phosphates. those advocating DSB's and looking for reasons for why systems go bad, would not want to admit it was the build up of phosphates in the substrate that was disturbed. if this were the case, then what they were saying about how the DSB works would be wrong, which it is. there is a slow migration of phosphates downward, not upwards in a substrate.

do not get me wrong SO2 is not fun stuff, but they ways i have heard tanks crashing from a disturbed substrate, the affects match a sudden phosphates influx more than a release of something as deadly as SO2.

just my .02,

G~

 

[rlpardue]

Phosphate also build up on the surface of live rock. I bathed 50% of my rock in muriatic acid, but left the other half alone because it was encrusted with various SPS corals and such. Now, 9 months into my new tank, the acid-bathed rock is 100% GHA free and the rest of the rock is generating annoying tufts of the stuff. It's like night and day. Hanna says my phosphates are at 0.04ppm and I run high capacity GFO, use a massive skimmer and many natural filtration methods.

 

[Reefin' Dude]

the reason why you need the GFO is because of the substrate. that is the part that is hard to understand. calcium carbonate structures act as phosphates sponges. bacteria are able to remove these bound phosphates from the calcium carbonate matrix. leaving a new binding spot. the object is to get the level of inorganic phosphates in the water column low enough to keep the bacteria in charge and not the calcium carbonate. with enough flow to blow away the detritus formed from the process of cleaving the P from the LR the LR is self cleaning of P.

with a calcium carbonate based substrate the amount of P in the water column is as high as the ability of the substrate to suck up the P. in the beginning it not that bad, as the substrate ages the rate at which the P is migrated downwards through the substrate is slowed, which slowly increases the available inorganic P in the water column. as with any sponge, it works the best when clean.

using calcium carbonate as a P sponge is well understood by those running BB systems and they use this knowledge to create low P systems. there is nothing wrong with using a substrate as a P sponge as long as its limitations are known and replaced/cleaned on a regular basis to keep it operating at optimal levels. BB people just do not see the need to have something else to maintain. it just makes sense to the BB people to remove the detritus before it is broken down by the bacteria to release inorganic P that could then be incorporated by the calcium carbonate, to start the whole process all over again. the less total P in the system, whether it is inorganic or organic the better. obviously this depends on the trophic level one is trying to emulate in the system.

G~

 

[Nammy]

5 or 6 years is not very long in the life of a reef tank

Agree totally!
Do to my military career I never lived longer than 4 years at any one place. I always had a great looking tank (to me anyway) with my style of DSB and never ran a skimmer….mind you never kept SPS, mostly Softies an LPS.
Everything grew like crazy and never had any algae blooms or water quality problems. Ok the occasional cyano but that's it. My maintenance was to a minimum; never cleaned the sand area but I did do my monthly water changes.
So I would say in my experience, 4 years was not enough time for things to build-up to a point where it caused me any issues….or maybe it was my DSB???

My style of DSB was more of a “Deep mixed Substrate Base” where I used a combination of aragonite sand and ¼-¾ size crush corals, and some crush shells. (Well mixed) In my mind the larger pieces would create pockets which would allow for isolated oxygen free areas.
IMO, with a DSB done this way, if for some reason the substrate was disturbed to the bottom; any amount of hydrogen sulphide accumulated within that portion released in water column would be minimal.
My DSB contained both aerobic and anaerobic areas which is what I was looking for.
(I god I hope I don’t get hammered for this post :lmao: )