I bought a new heater the other day for my 2.5 Gallon tank, its a Tetra Whisper Submersible heater. It LOOKS nice, but it doesn't seem to keep the water at 78 degrees like it says it does, since I've put it in the water has decreased down to 76! The instructions claim a red light will turn on when it is heating and turn off when its at the optimum temperature. Could it be that my stick on thermometer is just off by 2 degrees? Or is the heater just bad? I'm guess that my thermometer is just off. I stuck my pinkie in and the water still feels really warm. I guess I'll have to watch the temp to see if the heater maintains it at the 76 the thermometer claims it to be, then I'll know which is bad.. Argh!
Product Page: http://tetra-fish.com/sites/tetrafis...id=1276&cid=63