My Tank crash - Hopefully you can learn from my experience :(

[ComfortablyNumb]

My own experience also indicates the stated cause is "fishy". I had a tank go almost 2 full days without power... with one minor loss of a fish that wasn't doing that well anyway. All other inhabitants lived, although 3 of the 14 later got ich. The temp in the tank dropped a few degrees (which actually assists with o2 uptake) while I had a blanket over it for about 40 hrs. A dark tank, as presumably the OP's tank was as the claimed outage happened at night, would also use up less o2 due to the relative inactivity of the fish.

My apologies...but colour me sceptical.

[rsisvixen]

Originally Posted by ComfortablyNumb

A dark tank, as presumably the OP's tank was as the claimed outage happened at night, would also use up less o2 due to the relative inactivity of the fish.

While true fish might use less oxygen at night, a tank also has less dissolved oxygen at night with the lowest levels of dissolved oxygen just before lights on. All photosynthesis is halted without light, and algae and zooxanthellae will use up dissolved oxygen and release carbon dioxide at night.

[SeaHorse_Fanatic]

Originally Posted by rsisvixen

While true fish might use less oxygen at night, a tank also has less dissolved oxygen at night with the lowest levels of dissolved oxygen just before lights on. All photosynthesis is halted without light, and algae and zooxanthellae will use up dissolved oxygen and release carbon dioxide at night.

Exactly. This reverse-photosynthetic process exacerbated the low dissolved Oxygen issue and would have made things worse, NOT better.