Sorry to make another post so soon after my other one, but I seem to be having temperature issues in my tank. I have a 25 watt heater that I set to 77 degrees, and the air in my room is 67 degrees near the tank. (quite chilly, yes). The tank temp seems to have settled at 80 degrees, is this to warm for a guppy and a platy? I also don't understand why it's so warm in the tank since the heater is set at 77, I think the light might be heating the water too. Does anyone have recomendations for a light that wouldn't heat the water?
Also, my guppy doesn't let the platy eat at feeding time, even though they get along really well otherwise. I tried just scopping the guppy up in a big plastic cup and feeding him in there and feeding the platy in the tank, and it seemed to go smoothly. Are there any issues with doing this? Is it really cruel to the guppy? He's happy to eat in the cup so I don't think it's stressing him out, but maybe I'm wrong.
Thanks!

Did you calibrate it by the thermometer or just by the little tick marks by the knob? I've found those marks on mine are completely worthless - both tanks are 75F, but one is set under 70 and the other isn't even marked. Adjust it down a tad each day until it settles where you want it. Trust the thermometer, not the heater.