I have an established 90 gal aquarium with 4 small SA/CA cichlids (All under 5 inches) and a 6 inch jaguar cat. I am running 2 Rena Filstar XP3 and a Penguin 350 Power filter(I was only running mechanical filtration and biological filtration, no carbon). I feed twice a day (Hikari bio gold and mix in some occasional spirulina pellets or freeze dried shrimp/blood worms). I noticed about two weeks ago my tank started to get really cloudy so I started testing my water daily and was still getting zeros across the board (Ammonia, Nitrite, Nitrate). After 4 days of testing water twice a day and getting zeros, I went back to testing twice a week. At the end of the week I tested ammonia and was shocked that it was at 2ppm!! (Nitrite and Nitrate 0). I freaked out and started doing daily water changes (30-40%). After a week of doing daily water changes and adding a bag of carbon to each of my filstars, my ammonia will not go below .50 ppm but my water is crystal clear. My Nitrite and Nitrate have never spiked, they still remain at 0. Every day when I check ammonia it is either at .5 or 1, I do the water change and it goes down to .5 but never below. I figured when it first spiked, that my jag cat died since I only ever see him when I move stuff around to gravel vac, but he was alive and well. I am getting frustrated and sick of daily large scale water changes, its breaking my wallet ( I use seachem stability and prime). Can anyone offer advice or help??