How cold is cold?


New member
Hello, I have a question regarding temperature. I moved my fish into a big new 300 gallon tank but it's in the attatched garage for testing and and it's a bit cooler out there.

Waiting on a new heater and pumps the tank went to 68-69 degrees for about a week straight. Now lower than 68. I've got it sorted out now and it's up to 74 degrees but I was wondering if the fish can be harmed or is it terribly bad for them to be at 69 degrees for so long?

Everything seems fine but I guess I've never considered the lower limits of a healthy tank's temperature before and wanted to know. O2 obviously insn't a problem.

How low does it have to be before it's a problem for your FOWLR tank?

Thanks for any replies.


New member
for typical tropical water fishes, 70 is pretty much the lowest you want to go. i would recommend that you raise it SLOWLY asap (no more than 2 degrees per day).

it's surprisingly costly to heat a 300g to 77-78 degrees in the winter. my electricity bill would be $80 more in the winter months just from the additional electricity needed to heat my 225g.


New member
IMO it should be fine. My tank that's in my garage is around 68 in the winter (no heater) with no issues to my fishes.