Deep sand bed

[JohnK]

"If you want a DSB for denitirfication, they yes it is usually reccomended to have a bare minimum of 3" with 4 or 5 being better."

Studies presented at several meetings (Macna I believe) have shown that the anoxic environment needed can be created in less than a 2" substrate. Any increase in depth after that will not improve efficiency.

Yes, I remember that study. For a few reasons I am suspect of the results to some extent. I was referring to the traditional reccomendation of 3"+, but as with everything in this hobby there are differeing opinions and interpetation of facts......

Do you by any chance know where to find the write up on that? I know it's out there, but don't recall where???

And YES there has been much debate about DSB's...... Search, read, read some more, form your own opinion. There is little consensus on this one

 

[me2003]

In an earlier post. I think a poll would be interesting also.

An Experimental Comparison of Sandbed and Plenum-Based Systems. Part 1: Controlled lab dosing experiments

Robert Toonen, Ph.D., Christopher Wee
http://www.advancedaquarist.com/2005/6/aafeature

 

[lisa foster]

I wish I knew how to set up a poll

 

[JohnK]

Thanks for the link, I needed to re-read it to refresh myself about why I am skeptical.

In short, my criticisms come from two points.
1, the experiment only ran for 111 days. Arguably not enough time for a DSB to even become fully established
2, none of the experimental tanks ever reached zero or near zero nitrate. (I take this as evidence to support criticism #1)

Also the substrate used appears to be more of a crushed coral than sand. Arguably not very condusive to an effective DSB. That would be condusive to increased phosphate levels in the substrate (as the water testing shows).

Sorry for the hijack, I was feeling the need to justify my poo pooing on the only actual science ever done on this topic

 

[me2003]

It is reasonable to point out perceived flaws in any study.
I would like to point out there is no way to defend against a
temporal (time based) argument. It was not measured enough times
or long enough. If you were to do a study for a year, I could say
it is not valid it should have been run for two years. The second
is this is the only valid data and all others I have seen are just pure speculation.
I have had several tanks with sand beds less than 2" with nitrates
at near zero. There is no valid data showing a correlation between
DSB and nitrate levels or healthy aquariums. I can not attribute my
success with the depth of the sandbed. You can't either even if you
don't agree with the study.

In short, my criticisms come from two points.
1, the experiment only ran for 111 days. Arguably not enough time for a DSB to even become fully established
2, none of the experimental tanks ever reached zero or near zero nitrate. (I take this as evidence to support criticism #1)

 

[me2003]

I added a poll. It has to be in a separate thread.

 

[JohnK]

It is reasonable to point out perceived flaws in any study.
I would like to point out there is no way to defend against a
temporal (time based) argument. It was not measured enough times
or long enough. If you were to do a study for a year, I could say
it is not valid it should have been run for two years. The second
is this is the only valid data and all others I have seen are just pure speculation.
I have had several tanks with sand beds less than 2" with nitrates
at near zero. There is no valid data showing a correlation between
DSB and nitrate levels or healthy aquariums. I can not attribute my
success with the depth of the sandbed. You can't either even if you
don't agree with the study.

I agree with everything your saying, with one exception... The use of the word "valid".

If we're looking at the study to examine the difference in DSB's vs SSB's denitrification potential, but the study hasn't been run long enough to measure that, then the study is not valid for that question. It is likely reliable, but not valid for that.

You have had low to zero nitrate with a SSB, I have had the same with DSB. The study did not get there, so I'm calling the conclusion that there is no difference suspect. Not saying it's wrong, just saying that it appears that the data is inconclusive.

Again, I agree with all you said, I'm just splitting hairs for fun