Hiya!,
I'm new to this forum but I've been reading it for a while
I have a 170L tank with an internal filter, and a 200w heater. Its currently got about 15ish platies in it, which came from my pond outdoors. So, they're pretty used to the cold. I'm running a heater in the tank as its making the house too cold without it!
my question is: my heater seems to be cooking my fish. I set it last night to 22 degrees, and when I got up this morning the tank thermometer showed the tank was at 26 degrees, but the heater still hadn't turned itself off. I assumed the themostat was naffed and turned the heater off (it was secondhand). Today I went a got a new heater (200w Visi-Therm), and set it to 26 degrees when I put it in the tank as I didn't want to drop the temperature to fast and shock the fish. 2 hours later and the tank is at 28 degrees, heater still churning away. Turned the heater down to 22 degrees and the thermostat turned it off.
Whats going on? Is the internal filter kicking out enough heat that I don't need the heater running at all?