Hello! New to this. Got a 20 Gallon Long fish tank. i've had it operating about 2 - 3 months now. I have 6 tetra. 1 Cory Catfish and a sucker fish that only comes out at night. I have a 200 Gallon/Hr filter and 50 Watt heater temp at 75/76 ish. Sand and gravel mixed together bedding. Should I get more fish? They all seem very happy so far and doing very well. I do regular water changes and add Prime Ammonia remover and StressZyme bacteria about twice a month.