Hi there - Newbie here! I recently purchased 4 Mickey Mouse Platties - 2 male adults and 2 fry (I couldn't resist, they are adorable). The store employee said it was okay to keep the adults with the fry, but after much research - I've discovered the adults can and will eat the fry so I've moved the fry to a 2.5 gallon tank with filtration. I'm worried about the water being warm enough for them - can I put a 25 watt heater in this tank? The tank is not glass. Any input would be sooooo welcome- thanks!!!