Deep sand bed idea

[mgreefer]

I have a wet/dry that I use as a sump. I do not use any bio balls, I rely on live rock in the display. The bio ball chamber currently houses heaters, etc.

I am thinking of filling the bio-ball chamber (8H X 12W) with sand and use as a deep sand bed to control Nitrate. Water will trickle through the drip plate onto the sand, then flows from underneath the sand through the baffles into the second chamber which has the return pump. I will make sure that sand does not migrate to the second chamber.

What do you guys think, will this work or would it be too much flow for the anaerobic bacteria to thrive, is 8? too deep, any draw backs or issues that you might think off or any better suggestions.

Thanks.

[jadidaskv]

my brother is running a wet/dry w his system. what we did was drill a bunch of holes in the bottom of the return area. then put the wet/dry inside of a 30g sump and filled the water to the factory max fill line on the wet/dry so far everything is working good. we are also wondering if your idea is a good one.

[John K]

If the water is flowing through the sand it will not function as a DSB, the low o2 levels will never happen. If the sand is on the bottom of a chamber in the sump and the water is flowing over it, it should work as a DSB.

[mgreefer]

If the water is flowing through the sand it will not function as a DSB, the low o2 levels will never happen. If the sand is on the bottom of a chamber in the sump and the water is flowing over it, it should work as a DSB.

I guess I don?t understand the physics of this, if the water is flowing over the sand bed, how would the nutrients and/or water column reach were the anaerobic bacteria is all the time, I think 3 to 4 inches down in the sand bed. Wouldn?t it be stagnant since there is no exchange or circulation?

Thanks.

[LockeOak]

It's impossible for there to be absolutely no exchange, the water is continuous from top to bottom. It might be slow, but there is exchange between the top and the bottom simply due to mixing, the nitrates move from the high-nitrate concentration water at the top to the nitrate sink created by the nitrate-consuming baceteria.

[John K]

diffusion. Areas of water with differences will move toward equilibrium, it just happens slowly. With a DSB, you don't want "stagnant", but you do want close to it so to speak..

[jadidaskv]

so put the sand on the bottom of the sump with some live rock, and with the wet/dry in the sump should i take out the bio balls and replace with rock since the bio balls house nitrates?

[SaltCreep]

There is a thread on this topic that's about 50 pages long (and 4 years old )on ReefCentral.

I read the whole damn thing.....:eek:



What you are thinking of is an RDSB or remote deep sand bed, as opposed to DSB which is just deep sand in the display.

The example used in that thread was a store that added a 55 gallon drum of sand to their 2000 gallon system and then nitrates dropped to near zero.

People began using buckets filled with sand to do the same thing on a smaller scale.

The key was to have strong flow of post mechanicaly filtered water across the top of the sand.


In the end, it seemed to work for many people and didnt do anything for some.

I am thinking of doing the same thing with a square bucket of Kolorscape in my sump.

[John K]

Yes, you do want to get rid of the bio balls.

It's not that they house nitrate (unless maybe a bunch of detritis is allowed to get stuck in them), but rather they process ammonia and nitrite so effectively that it throws the process out of balance. A lot of what could be pulled out by skimming gets broken down into nitrate insted of being removed. (there are other processes related to this but...) Overall the goal is to have a very nice blance between nutrient export and nitrification and de-nitrification. De-nitrification is generally the most limited part of the process, so if there is too little nutrient export and or too active nitrification, the de-nitrification can't keep up and you get accumulating nitrate (like in many older reef set ups and fish only systems).

Not to say you want ammonia and nitrite accumulating in the water, just saying that with strong skimming and active algae growth and harvesting (via refugim) much of the various nutrients may be removed compeltely before they become nitrate. Wet-dry's / bio-balls more or less encourage the opposite of the above balance by doing their jobs too well. Very few if any reef set ups use wet drys any more.

(and going back a bit, DSB's serve to provide a signifigant increase in the potential amount of de-nitrification potential a system has).

[RedTide]

In addition to other comments, 4" is shallow for a DSB. also, the exchange from water current is at the surface of the sand, not from top to bottom. I highly recommend Delbeek & Sprung's "The Reef Aquarium Vol III" to explain each of the various methods.

From the sounds of what you're describing, I agree that it will not contribute to Nitrate reduction.

[JavaJones]

Would a lot of low density, relatively porous reef rubble work better...with each piece maintaining its anaerobic bacteria deeper within the individual rubble piece? This will allow for faster water flow through over a much larger surface area than the presumably flat top of the sand bed.

[John K]

That would probably add some de-nitrifying potential, but not very much. If anything, with that approach I'd say use good sized LR chunks insted of rubble (so there would at least probably be more inner areas that would get lower O2 levels).

I would surely think that an area of deep sand would have far far more low O2 area than a similarly sized pile of rubble or rock. Not to say you need a DSB, and also not to say it's bad to have LR in the sump, but it's a question of your goals.

[Sean Irwin]

The thread on RC would definetly help, but in case you don't want to read all 50 pages of it... The efficient conversion of nitrate to nitrogen gas is directly related to the amount of anaerobic, dinitrofying (sp?) bacteria. The more surface area you have the more space for denitrifying bacteria to colonize. Sugar sized sand will provide you with the greatest surface area of any substrate. Conversion of nitrate to nitrogen gas must be carried out without the presence of oxygen. Oxygen and nitrogen are relatively close on the periodic table and oxygen effectively "poisons" the denitrifying process. That is why you cannot have water (carrying oxygen) flowing through the sand. The deeper the sand bed the better as this will encourage conditions where oxygen is excluded from your sand bed.

[CaptainAndy]

I never had much luck with the DSB - probably because I had toomany fish. However, rather than using the space for a DSB you might be better off with a refugium with chaeto. I've been using this for about 6months and my nitrates and phosphates, which were always tough to control, are always zero.

[Reef55]

Another item from that thread is the minimum recommended depth is 8 inches.

[JavaJones]

I set up my 29G refugium with a 6-inch sandbed (on a system with a relatively high bio-load with a total of about 120G); the nitrate levels have remained consistently low even with a rather neglectful attitude to water changes.

[mgreefer]

Thanks to all of you for providing advice/feedback, I now understand the concept much better. I apologize for posting the question on 2 forums which caused confusion and frustration to many of our members wouldn't happen again.

Again thanks for all the feedback and advice.

[reefinghabit]

wow all this, just buy a reef sump with a micron sleeve. do the live rock and sand in your main aquarium. its plain and simple get a protien skimmer to.

[Reef55]

wow all this, just buy a reef sump with a micron sleeve. do the live rock and sand in your main aquarium. its plain and simple get a protien skimmer to.

It's not as simple as that. Most tank sandbeds are only up to 4" deep, which we had a speaker recently that talked to that subject, and that 4" of depth is not quite enough to get a complete nitrification cycle. 8" of depth is the recommended minimum for complete nitrification, which very few have in their display tank. Setting up a RDSB in a bucket is a cheap, effective, simple solution that can fit under a stand to provide this filtration.

[wsonner]

It's not as simple as that. Most tank sandbeds are only up to 4" deep, which we had a speaker recently that talked to that subject, and that 4" of depth is not quite enough to get a complete nitrification cycle. 8" of depth is the recommended minimum for complete nitrification, which very few have in their display tank. Setting up a RDSB in a bucket is a cheap, effective, simple solution that can fit under a stand to provide this filtration.

Another reason to do it in a vessel separate from your display tank is that I have found it a pain replacing the sand as it dissolves over time without really mucking up the tank. I think I'll try this method on the next tank.

[Sean Irwin]

A remote bucket is a very good idea. If you ever experienced a power outage you could cut it off from the main tank, and not worry about the aerobic bacteria in the upper levels of the sand consuming all your tanks oxygen. If you wanted to really reduce nitrogen and phosphate levels (and you have unlimted space. You could create a series of refugium vessels:
1. Filled with cheato and some live rock
2. A deep sand bucket (unlit to prevent algae growth)
3. A unlit or cryptic refugium

[reefinghabit]

ok well my sand bed is 4" deep i see tons of air bubbles wich i know to be nitrogen bubbles the end result of denitrificatioin. ie nitrate to nitrogen gas. remember the deeper the sand bed the higher the risk of hydrogen sulfate gases. i have actually built them up in my own sand bed, if its not well maintained. and it smells horrible, besides it can kill your fish.you will notice layers of dark black or gray. this is where the bad gases are