B&G,

Yes, the Pacu will die unless I have an overwintering capability in place by about Oct. 1. I'm working on that also.

From just a quick look it seems to me that a heater for this outdoor micro-pond would be very expensive on a recurring basis compared to an indoor overwintering capability.

My objective with the Pacu is to study it for a possible grass carp replacement in my ponds, in the manner of Tilapia, i.e. stock them in spring, let them eat vegetation during the growing season, then harvest them before they die in fall. The trick for this to be effective, I think, may be to grow the Pacu inside until temps warm and they reach a size where they can really effectively consume weeds. I like grass carp but see a lot of undesirable characteristics in them...always looking for a better way.

The Rios,GG's, and golden BG will all do fine in there during the winter....except the Rios may have low temp problems, but that is part of the test also.

If I can't get the overwintering capability in place, I will still get some time in on observing the Pacu's behavior.

Thanks again for your info. I'll use that rule of thumb (one inch per gallon).