I see your point Fred but I have an example for you of that effect. A local club member believeing in the DSB AND Plenum theory had such an accident when we had the floods a few years ago in 2002 or 2003. His system remained down for about 5-7 days. In that time his system developed many problems one of which included a huge release of hydrogen sulfide which was very apparent in the odor.
Along with that were many other problems which essentially wiped out his grow out tank of frags. In there he also had animals to turn over the sand bed naturally.
I won't argue the point but a healthy debate is always good. Because of the tremendous bioload over say a rock substrate tank, I think the edge of the envelope gets pushed. I know some people have success with DSB setups because I've seen it with my own eyes. But I also see more people that develop problems which has wiped out there entire tanks.
Why it works for some and not others I don't know.
I will also say that it is probably a closer to natural enviroment though (DSB).
That one example was not my only experience with DSB either. I tried one on my own using seeded sand in a new setup which wound up wiping out everything even after a month and a half of bacteria build up.
Had I had a good experience with it and everything grew normally I would probably have a different opinion or maybe even swear by it, but I dont' see any advantage of one method over the other to be honest and more than a couple results have been less than noteworthy.
I'm not saying you or anyone else with DSB is wrong I just think that DSB AND Plenum is an antiquated idea. Neither of us are right or wrong it's a matter of results and opinons from opposing points of view

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