That is really interesting spiff! Do you know if there were any areas where anaerobic bacteria could live?
That stuff breaks down nitrates too and often goes overlooked. Things that or porous and somewhat solid can house anaerobic bacteria ie: clay pots, bricks, etc. They get housed where there is no oxygen (like in the center)
This also occurs with to deep of a sand substrate and eventually sulfuric gAS(or something, i'm not too sure) will build up in large pockets under your substrate. But i digress. Thats really cool about your tank, i wish mine did that haha. but it did go a year in the 100-200 range
Well, I guess my UG might have some anaerobic spots, like under rocks where it doesn't get vac'd with every water change. But I keep things pretty clean, so I kinda doubt it.
Isn't anaerobic substrate usually indicated by the presence of fine bubbles coming out of the gravel every once in a while? I never have that happen.