My betta has been laying on the bottom of the tank for a few days now and this time when i came home, I found him sucked up against the filter i nudged him with the net and he swam away, thankfully, but then he just went and layed on the gravel not moving. It's been hot lately and my filter generates a bit of heat so I've been turning it off to let the water cool but the water still went up to around 87 degrees. My betta, Matcha Custard, lives in a 2.5 gallon tank with 3 neon tetras with a bit of aquarium salt, no heater yet because of the hot weather, a filter, and 3 fake plants. He also has a torn back fin with the tear all the way to the base of the tail. I've been giving him betta fix and feeding him pellets. I've had him for about 3 weeks. I'm very worried about him and I hope someone could give me advice.