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[madmac]

Black substance in sandbeds

I am definately sure that any aquarists who have kept sandbeds before would have come across the statement that a black layer would be formed. Some say this is hydrogen sulphide, some say this is cyanobacteria. Actually, this black stuff is none other than FeS or Iron sulphide.

Iron sulphide itself is a brown precipitate and due to the intense colour, we often perceive it as black. All sulphides are toxic to organisms and thus, this chemical is not good for reefs.

This compound is formed by sulphate reducers which being anaerobic bacteria, usually thrive under mats of the cyanobacterium Lyngbya sp. or in any anaerobic region. Thus, in anaerobic regions of sandbeds, a "black" layer of FeS is formed.

FeS can be oxidised in the sediment by MnO2 or maganese oxide into FeOOH, S, Mn and H2O. It can also be oxidised into sulphuric acid by autotrophic or mixotrophic bacteria and will be neutralised by calcium carbonate into calcium sulphate.

All in all, the black substance is not much of a worry BUT it indicates that the sandbed has a totally anaerobic zone and this should be the main worry of aquarists

what happens before the FeS is produced? What gets released during the sulphate reduction?

Biological Sulphate Reduction

The above link and other links within are truly just great. For those who like to have a more than surface understanding of things taking place in sediments, pls take some time to go thru' them.

[blueheaven]

That's a good link

I usually derive my information from reading these science journals

It wasn't easy to simplify it ya know!!

[bluezing]

nice info bro! hehehe

in that case..what is the recommended livestock for the sandbed?

cos im still quite confused on whether we should disturnb the sandbed once in a while anot?

[cdckjn]

Thanks for the list of outstanding articles. Cheers.

[blueheaven]

nice info bro! hehehe

in that case..what is the recommended livestock for the sandbed?

cos im still quite confused on whether we should disturnb the sandbed once in a while anot?

Actually, I find that small brittlestars, worms, flatworms and pods make good infauna

However, the sad part is that the LFS do not have these recharge kits so what I did was I grew my own infauna

[bluezing]

ok thanks!~ noted on that bro~