[Delphinus]

I guess I'm not hugely worried about it in that tank at this point. I don't forsee that 72g housing the ritteri for a period beyond the next five years anyways, so, .... If I have to replace a DSB every 5 years ... the tank will probably be torn down well before then, or maybe I'll move to a different house by then ... at some point something else is going to dictate that I do something different anyways.

I'm just thinking out loud here ..... One other thing to maybe consider, that I think could be valid, is that sometimes a DSB is good for reasons beyond just the denitrifying. For example, I am planning on redoing my carpet tank, and I plan on putting 4"-5" of sand in there. The choice of this is dictated by that a deep sand bed of fine particle size is the appropriate substrate for a carpet. Whether it denitrifies, or breeds bugs on the side is almost immaterial ... it should be there for the benefit of the animal that is looking for it. Hmmm, again, just thinking out loud here ... It seems to me another example would be this: a bare-bottomed tank would be a terrible home for a jawfish .... although a fine particulate DSB would also be nearly as useless for that fish .... for that fish you'd want a deeeep sandbed but with quite variable sized grains ranging in size up to the "small pebble" size. So again the choice of animal dictates (at least in some cases) the choice of substrate.

I would imagine that anyone attempting to house, say, garden eels, would need like a 12" - 16" sand bed. (Yikes!!!!)