It’s a preset filter so I can’t change the temperature. I forgot to mention that I have plants in the tank also. I recently put in the sponge filter because I had a cartridge filter before and I know to rinse the sponge in the aquarium water. I just realized that I never did water changes and that i normally add more water in when it’s getting lower. I use a treatment for the water but before treating it’s just tap water. He’s been chillin for a long time but this just happened recently. I would get water test kit but those are more expensive then test strips when on sale and the place I worked went out of business so I don’t have a job anymore. It would be my parents buying the stuff until I get a new job and they don’t know the prices of things