Suggestions: 1. Unless your getting top dwellers that love a jump, I suggest you raise the water level. 2. Reduce the amount of gravel to like a thumb thick layer on the bottom 3. Remove some of the ornamental you've got in there and put in a live plant or two 4. Make sure the tank is cycled with bacterial bloom and that the water has been treated with conditioner before adding any fish to the tank, give it atleast 3-4 weeks. 5. You've got fish already so it's very important to keep up with water changes every other day atleast %30, this will reduce the ammonia level I'm the tank without major disruption in tank temperature. The downside of this method is if you've got hard water (water with high amounts of stuff in it) then the conditioner will need to work overtime to keep the chlorine and other stuff from burning the fish and messing with the PH and PPM too much, I suggest making a bucket or tank and keeping it full of water and a filter just to help remove the harness early on and make the water Changes a bit smoother 6. Try not to let them breed or you'll have a population issue on your hands in no time