Ice? Snow? It’s been almost 30C here the past few days!
My biggest concern with keeping fish outside is how to prevent them from overheating, while keeping them warm. It might be too cold in the shadow, but it will certainly get too hot in direct sunlight.
I don’t know how the climate is where you live, but our Dutch weather changes it’s mind every few moments. It might be a nice temperature today, but tomorrow night it could be freezing, so to speak. Even in mid-summer, the temperature swings like it’s drunk.
A fish of tropical origin will probably dislike such changes. Paros don’t need high temperature (I don’t use heaters), but I think they like it to be constant.
You could give it a try, however, if you have sufficient numbers of fish.