The jack dempsey and the blue cichlid are sweet. Do you have a heater? tropical fish won't last long without one, you can get away with it in saltwater but any temp fluctuations by a degree or two can screw everything up. If you turn off the bubbles the tank won't stink as bad since you're not circulating the stench. Also until bacteria forms on your filter media, you're tank will stink. The bacteria eat the crap.
Really? I have not had a heater on my tank since I have owned it. Which has been for about 4 years. I have had very good luck with my fish living a good while. It never drops below 65 degrees. I only have Tetras and a Cory though.