I have a Aqua One 90 Litre aquarium, I was wondering how many fish (max) could fit in it? It has a powerhead with the cartridges, and 2 18Watt each lights. It is already running and has had fish for well over 6 years. Right now I am in the process of adding plants (Anubias, Stargrass, Java moss, Java fern, Cyperus helferi, pennywort), and would like to add as many as possible to it. I currently have small fish in it, around 15 or so. What could I do to accommodate more fish, and to get healthy plants. BTW I will not add c02 to the tank. Thanks