Container pond in winter time...

since its only 20 gallons if you can bring it inside and it gets cool enough that you are concerned, then I would bring it in

danios are more tropical fish so if the water temp drops too much they probably wont make it

I'd bring it inside.

Only "coldwater" fish (goldfish, koi, etc) can usually survive long when the temps drop down under 50F, and it will definitely get much colder than that in San Antonio.

Thanks guys. And wow, glad I asked last night, cause its apparently getting cold tonight and might break freezing. I had an open tank in case I needed quarantine (been buying fishies lately) so I put them in there.

...I found a dead fish on the bottom, a fresh one, that wasn't any kind of fish I ever had (?!?!?!). I mean, the random snails make sense, but... Where did that fish come from? O_______o??? I also found part of my dog's collar that went missing long before I put those fish out there. Strange little guys...


On the plus side, the ONE little plant I put in there months ago is now a BUNCH of huge ones. (I think its the sagitarria. Well, regardless, I have plenty of it now.) And yay, after its been in there a while disease free, I might transplant some cause I have alot in one little hex.

being that most tank heaters are made to be submersible i don't see why you couldn't use one outside, as long as where it actually plugs in is weather proof. A cover of some sort (like a mini green house made from clear plastic and thin wood) might help it keep the temp up enough that the heater wouldn't have to run non stop.

My mom put two aquarium heaters in her 1oo gal. pond (goldfish and platys of all ages) She lives in Killeen tx. north of you. No cover and lost none of her platys. she has been doing this for two years now. But I think she is pushing her luck. I do not know the brand etc. of her heaters,but they are large ones. She also cuts off her waterfall during freezing weather,and adds biozimes.