Originally Posted by untamed (Post 684663)

Low oxygen. That would be a guess, except for the knowledge of power failures which make that guess an almost certainty.

When you get running, you have to simulate that power outage again. Watch what happens when you turn the power back on. Do ALL the pumps come back on? Does the skimmer come back on? Do you have a skimmer? If not, this episode suggests that you should because they will add O2 to the water, especially after a power outage.

The other thing you might need is a battery operated pump that will bubble or move water during power outs.

Originally Posted by RedCoralEdmonton (Post 684681)

Probably too late now, but we don't charge anything to test your water, if you ever need a second opinion, feel free to come in.

Related to your post though, I would bet money on a O2 shortage, do you have a sump? If not, this is probably the cause, tanks without sumps can run fine under optimal conditions for years, but all it takes is that momentary lapse in stability to throw it off..... As others have stated, try and simulate the event and see what happens.

Steve