Hey guys, I have a bit of some questioning to whoever is listening. So I have a 75 gallon freshwater planted tank with lots of fish. (rainbows, small tetra, a 7in pleco, Siamese algae eaters. a Bolivian ram) And it's heavily planted with dirt as substrate. Ok, so about a year ago my heater (I got used when I bought the tank of a dude) stopped working. It still sits in the tank with the cord plugged in and the light is showing, but it doesn't heat the water at all. I don't know what to do? The water stays at around 65-67 degrees F. But the fish don't seem to mind it much ( or so I think). I recently (yesterday) bought 2 more rainbows and the B. ram and took 2hours to float the bag and acclimate them because of the temp. changes. So I made this post to generally ask what a heater can do to help out my tank? Like: Does the proper temperature (70-75ish) really affect the way the fish grow and eat? will it reduce risk of infection and sickness to the fish? and also, will it help my plants grow any better? or will that be constant? Also as a side note my pleco has sort of stopped eating for like a week and his stomach has bloated a little, I fed him mashed peas and he has recovered. what could have happen? was this because of the heater issue? Again my temperature is around 65-67ish *F. Thank you! any little help can really help me out thanks.

P.s. if you can, please recommend any good heaters you know about.

Again thanks a lot.