I think there are a lot of benefits to
not stirring, and just allowing the process that causes the black parts to continue. Though unsightly, it appears to be healthy for the aquarium. I found this link:
http://www.skepticalaquarist.com/docs/nutrient/sulfint.shtml
And this chart:
DeeDeeK, please forgive me for hogging up your beautiful thread, but I really want to try to keep the discussion on this topic open. There is so much to learn!
No, no, not all! Your input is exactly the sort of thing I was hoping to this thread would attract! And while my ego will probably sting if I'm criticized or soundly contradicted, I would still encourage even that input. I've just wanted a discussion to happen.
I'd like to point out that in the anaerobic layer there are species of bacteria which use nitrate to oxidize H2S, as well as there being aerobic bacteria which oxidize H2S. These are largely chemolithoautotrophic, similar to the nitrifying bacteria.
Diana Walstad, in "Ecology of the Planted Aquarium," states that rooted plants can take advantage of the solublized iron and manganese (if I recall correctly, molybdenum too) because they send their roots down into the anaerobic zone. Also, she states that the roots carry oxygen downwards with them in order to survive in the low oxygen environment and that they create an aerobic microzone where bacteria which oxidize H2S and other metabolic byproducts of anaerobic metabolism.
I've buried bunches of dead roots down and the bottom of the sand, next to the glass, and waited until they turned very black and were surrounded by pitch black sand, then pulled them out and given them a sniff. They definitely had some hydrogen sulfide smell to them so I know there's sulfate reduction going on but despite all the bubbles the sand bed burps up, I've never smelled H2S.
Here's a link I found interesting.
http://www.alken-murray.com/H2SREM6.HTM
I'd be interested in using their products to seed aquarium substrates.
Also, I'd like to try out the product, RTB 700, sold at this link:
http://www.microbialogic.com/rtb_700.htm
I've a feeling that RTB 700 must contain sulfide oxidizing bacteria in order to control odors, and since the bacteria are all non-pathogenic, I'd definitely try 'em in an aquarium in small quantities.
:thm:Anyhow, thanks Anoxia for the interest in keeping this thread alive!