RDSB

[suphew]

At the risk of starting an ugly thread again (please try and keep it nice) I have been reading a very long thread on reefcentral about running a DSB in a bucket, known as a remote deep sand bed (RDSB). I don't have any measurable NO3 in my tank, but do have some hair algae and a cyno problem, so there must be something there. I'm assuming that it is being used by the algae before I can test for it. So I'm concidering trying this out. The idea is very simple, very cheap to setup, and being remote can be removed easily.

To summerise the very long tread, there are a few significant differences between a DSB and RDSB that address usual potential problems.

1) The RDSB is setup with no light, usually in a closed container. The idea behind this is to stop algae and diatoms etc growing on the surface, this stops the sand clumping or the top layer becoming sealed. This means two things, first there is no requirement 'critters' in the sand bed to keep the top layers turning over. secondly fine sand can be used.

2) Because there is no need to support life in the RDSB the water fed in is filtered, either by mechanical filter on the input, or by using the skimmer output to supply it with water. The affect of this is it stops the RDSB becoming a nutriant sink, therefore eliminating/reducing the risk of it crashing.

3) Very fine sand is used, two reasons for this, it increases the surface area in the sand, and it reduces the likelyhood that any nutriants that get in are able to work their way down in to the sand bed.

4) The depth of the sand bed is limited only by size of container used. The thread recommends at least 8 inches, but there are larger setups using plastic rubbish bins with a couple of feet of sand.

5) A highish flow of water is used through the RDSB, the reason for this is the same as in your tank, to stop detrious settling on the sand.

6) The system can be 'tuned' and maintained, instead of using one large container 2 or more smaller containers can be used, allowing you to add more containers to increase the NO3 reduction, and containers can be removed and the sand replaced on a cycle (suggestion is yearly) so there isn't a sudden drop in NO3 reduction if you decide to replace the sand.

Here is the link, it is very long and a lot of the same questions being asked over and over by people who can't be bothered reading the whole thing.

http://reefcentral.com/forums/showthread.php?s=&threadid=595109&perpage=25&pagenumber=1

[wasp]

Sounds good to me Suphew, if you do this you must report back at some point with your evaluation af the method

What might happen if you pulled your existing sand is there would be an intial nutrient "bloom" due to nutrients released while you removed it, plus it will take some time for the rock to increase processing to make up for what the sand was doing.

I don't think an RDSB in a bucket would be as effective as one across the whole floor of the tank, but should nonetheless have benefits. Maybe positioning it so good flow moves over it would help to get good water contact.

[JoeBlog]

I have one. It's a 70L bucket filled with sand, kept in the dark, and has a high flow over the top.

I originally installed it due to a bad HA outbreak (zero readings of nitrate and phosphate on Salifert). I tried the dosing of vodka (a whole LARGE bottle of Absolute) with no effect. So, I tried the bucket. I also added the UV at the same time, so can't say which of the two drove the result, but the HA is gone.

[suphew]

Nice, I'm glad someone else is trying it.

What might happen if you pulled your existing sand is there would be an intial nutrient "bloom" due to nutrients released while you removed it, plus it will take some time for the rock to increase processing to make up for what the sand was doing.

I currently don't have any sand in my system, I sucked out the 1cm or so I had in my display a month ago, to see if it was causing my cyno problems. BTW the cyno regrowth has slowed down since removing the sand.

I don't think an RDSB in a bucket would be as effective as one across the whole floor of the tank

Agreed, but the shape of the container isn't limited to the typical round bucket, I guess a long trough shape would be better. Also its a bit hard to compare the two because an in tank DSB will have all sorts of stuff sitting on the surface reducing the water contact surface area, algae, microalgae, rock, etc.

[Feelers]

I dont get why you dont just use it as a nutrient sink anyway? Even with mechanical filtration and small grain sand it will still fill up with nutrients. This system of RDSB is quite similar to a fluidized sand bed (in terms of nutrient buildup).

Definately give it a go, I'm surprised so few people incorporate DSBs in this manner.

If it were me I'd want the dirtiest sandbed around, you can always disconnect & throw it away, any gunk that it pics up has been missed by your skimmer, but can feed pods etc.

[suphew]

Ideally you want to export the nutrients rather than leave then in the system where one way or another they could cause a problem in the future, in the case of a DSB there is really no way of knowing when the sink will become full. This may or may not cause it to crash, but either way it would need to be removed. Doing this without releasing all the rubbish into the tank can be difficult, and even if you can do it, the sudden removal of the DSB, then waiting a month for the new one to fully kick in is going to cause issues. Filtering the input and the high flow might not stop all the nutrients getting onto the sand bed but it will signifcantly reduce the amount so that it could be run for far longer periods with out having to worry.

In the thread quoted a lot of people thought it was similar to a fluidized sand filter, but this isn't the case at all, the idea is to have the in and out feeds both on top of the bucket/container the main flow of water doesn't go through the sand at all, if fact there is very little if any water movement in the sand bed.

[lduncan]

2) Because there is no need to support life in the RDSB the water fed in is filtered, either by mechanical filter on the input, or by using the skimmer output to supply it with water. The affect of this is it stops the RDSB becoming a nutriant sink, therefore eliminating/reducing the risk of it crashing.

DSB's work by sinking nutrients. If they don't sink, then they don't work. And the only way to stop them sinking is to vacuum them. In this case you want it to sink nutrients.

3) Very fine sand is used, two reasons for this, it increases the surface area in the sand, and it reduces the likelyhood that any nutriants that get in are able to work their way down in to the sand bed.

What's the sand for then, if you don't want nutrient to get into it? How will it work?

I've had a very similar setup to this before. Run it for a few months and then ditched it. After seeing the state of the sand, i decided i'd never do it again.

Layton

[suphew]

Maybe I should have been clearer on the application of this system, it is purely for the removal of nitrates by providing anarobic and anoxic environments while avoiding the problems of a standard DSB, like it turning into a nutrient sink and being actually in the sump.

[lduncan]

Maybe I should have been clearer on the application of this system, it is purely for the removal of nitrates by providing anarobic and anoxic environments while avoiding the problems of a standard DSB, like it turning into a nutrient sink and being actually in the sump.

But that process is one in the same.

If the bed is performing denitrification, it must also be sinking and storing nutrients.

Layton

[suphew]

No, not at all, from Anthony Calfo...

"it is a modest strategy and dependant on bioload of course. But so cheap to employ, and easy to remove if you don't like it.

My LFS finally tried this with a 55 gall tank full (nearly to the top) of sand with a good stream of water traversing the length of the tank. It was staggering how fast it reduced nitrates on a nearly 2K gallon system.

A 5 gallon bucket with a 60lb bag of sand filling it can do similar/remarkable work on say a 90-120 gallon tank. A larger plastic garbage can (kitchen size... 20 gall or so) with a couple hundred lbs of sand, etc.

The goal here is denitrification and buffering (if using aragonite).

There are not many other benefits... and not many risks either. Unlit and with a strong stream of water over it, its a fairly brainless application Cover it and keep it dark... there is little to maintenance to speak of for it. You can imagine that with the good water flow (key) or even mechanically prefiltered water... there is no way for this to practically become a nutrient sink, as the small fast volume of water cruising over it do not allow the settling/sinking of much solid matter over time."

[lduncan]

Can you reasonably expect nitrogen waste to get to the places required without phosphorous getting there as well?

The same bacteria which are performing the denitrification and nitrogen cycling, are the ones which are responsible for storing, migrating and cycling P.

They go hand in hand.

Layton

[wasp]

the sudden removal of the DSB, then waiting a month for the new one to fully kick in is going to cause issues.

Would it be possible to have 2 containers with a DSB, and just replace one alternately?

[lduncan]

that was one of the ideas:

6) The system can be 'tuned' and maintained, instead of using one large container 2 or more smaller containers can be used, allowing you to add more containers to increase the NO3 reduction, and containers can be removed and the sand replaced on a cycle (suggestion is yearly) so there isn't a sudden drop in NO3 reduction if you decide to replace the sand.

[suphew]

Can you reasonably expect nitrogen waste to get to the places required without phosphorous getting there as well?

The same bacteria which are performing the denitrification and nitrogen cycling, are the ones which are responsible for storing, migrating and cycling P.

They go hand in hand.

Layton

But whats your point? Of course there is going to be 'some' phosphate that gets there as well, when have there ever been obsolutes in reef keeping? The point of this system is that with the filtering and no light, pods, high flow, etc, the possible nutrient sink aspect is significantly reduced so that it doesn't need to be a serious concideration.

[lduncan]

What i'm saying is that it is ALWAYS a serious consideration, unless you are vaccuming the sand.

The thing is is that for the nitrogen benifits of the bed to occur, it MUST be sinking nutrients. You don't have one without the other.

It's the bacteria in the bed which mediate the sink / source cycles. The same bacteria which is performing nitrate reduction.

Layton

[wasp]

Seems a very reasonable idea to me.

The RDSB may sink phosphate. Excellent! Once it's time, the whole point of an RDSB is it is easily removed & changed. Maybe annually, whatever.

[suphew]

What i'm saying is that it is ALWAYS a serious consideration, unless you are vaccuming the sand.

What would there be to vacuum? The filitering and high flow is there to stop most solids from settling on the sand. Of course this isn't an obsolute, but if setup correctly there would be so little it isn't worth considering, this and swapping the bucket out every year.

The thing is is that for the nitrogen benifits of the bed to occur, it MUST be sinking nutrients. You don't have one without the other.

If you trying to address the whole cycle, then yes, but this setup is to only address the final stage, nitrate to hydrogen sulfide. The bacteria that do the nutrient reduction (here I'm talking about, ammonia-nitrite-nitrate) are different to to the anarobic/anoxic bacteria that this environment is targeted at. Again I'm not talking about obsolutes, there will of course be a small amount earlier stages going on.

[wasp]

That quote you posted from Anthony Calfo was interesting Suphew, I didn't think a 55 gallon DSB would deal with a 2000 gallon system so well.

The secret would probably be to have excellent circulation so that all water passed over it multiple times.

[suphew]

Yeah, there was a bit of conflicting information on how much flow, most seemed to suggest as much as you could have without blowing the sand out. But there was a suggestion that you measure the NO3 going in and out, then increase the flow until until the NO3 out starts to rise. But either way as long as the flow is high enough to stop anything settling on the sand I think it would be ok.

[lduncan]

What would there be to vacuum?

A LOT of detritus. Try it and see.

The filitering and high flow is there to stop most solids from settling on the sand. Of course this isn't an obsolute, but if setup correctly there would be so little it isn't worth considering, this and swapping the bucket out every year.

It doesn't work that way in the ocean, and it won't work that way in a tank. Try and see how much flow you need to achieve that. You'll probably find you won't have sand left on the bottom for very long ;-) Also bacteria are part of the problem in sinking this stuff. The nitrogen doesn't have to be in solid particulates for it to get there, and neither does the phosphorous. If you have nitrogen (as nitrate) in soluble form, then you are going to have P in soluble form too. Large amounts P will still find their way into storage there.

Best thing to do, rather than deny it's happening, is just recognise that you can't change that behaviour just by changing the flow over the bed. The only way to change it is by cleaning the bed. Then focus on replacing the bed, or adding more depth to the bed, before things change.

If you trying to address the whole cycle, then yes, but this setup is to only address the final stage, nitrate to hydrogen sulfide. The bacteria that do the nutrient reduction (here I'm talking about, ammonia-nitrite-nitrate) are different to to the anarobic/anoxic bacteria that this environment is targeted at. Again I'm not talking about obsolutes, there will of course be a small amount earlier stages going on.

It's all going on, it has to, otherwise the sandbed doesn't "work".

Also realise that the typical nitrogen cycle explanation you hear of ammonia -> nitrite -> nitrate -> nitrogen gas is not quite as straight foward as that.

Nitrogen is cycled too (just like phosphate) some is converted into ammonia some into nitrogen gas. Some of that ammonia is assimilated by benthic algae, some will be oxidised back through nitrite -> nitrate.

All these processes are going on so that the sandbed can do it's storage and denitrification.

Layton

[suphew]

Ok, how about this, are you will to admit that there would be (significantly)less detritus getting into the sand bed using this system over a normal DSB?

Do you also agree that this system would allow you to remove the sand bed and replace it as regular maintenance (say yearly)?

Therefore, even ignoring the other benefits (like no algae on/in the sand bed, no extra bioload, etc) doesn't this all but eliminate the chances of the sand bed crashing from nutrient sink overload?

So to conclude is cheap and simple to setup, likely to work well for what its designed to do (NO3 reduction), and low risk?

[wasp]

Suphew to be straight up, I don't know how much value you will get from arguing this with Layton.

He tried to have a DSB once but it failed in only a few months. This bad experience has coloured his view on the subject, he now does not have a DSB but specializes in telling everybody else how to run theirs.

Past experience and much wasted time arguing on this forum, and looking at what I've gained as a result, has taught me that the great bulk of what I have learned has come from talking to people who have succeeded at a method, rather than taking advice from people who have failed at it.

Over to you of course but wish I could reclaim some of the time I've spent arguing the toss over a method with someone who failed at it after only a couple of weeks but believes he is a world authority on it.

[suphew]

But he hasn't drawn me a graph yet :lol:

[lduncan]

Try it and see then.

You might be surprised.

Layton

[lduncan]

He tried to have a DSB once but it failed in only a few months. This bad experience has coloured his view on the subject, he now does not have a DSB but specializes in telling everybody else how to run theirs.

Actually wasp, it wasn't like that at all. You should stop assuming things like this.

Layton