ok so I have a 20 gallon tank with a Emperor 100 I think its the one that take 4 of the biggest cartridges i only run 2. It is for a 75 gallon tank. I also have a Fully cycled fx6 on my big tank I can add to if needed. But how many 2 to 3 inch cichlids can I keep in QT for 2 to 3 weeks?, in a 20 gallon tank. I see the fish stores with 30-50 in a 40 gallon Breeder. I want to do 18 -20 I will do daily water changes of 25% should I add the FX6 or just some more bio media?