i have 15 Malawi African cichlids, mostly haps with a few mbunas and peacocks, in a 60 gal tank with eco complete cichlid white sand substrate. I set up the tank about 5 weeks ago and slowly added a few fish at a time, most recently 10 days ago. The water parameters are all 0 ppm on amonia, nitrate and nitrite and the ph is about 8.0. Water temp is 82 degrees. Since yesterday most of the fish are hanging at the top with a few pointing their nose upward. The tank goes through periods of clarity and some slight murkiness. I did the most recent water change yesterday @ 25%. Should I do a larger water change? Seems my parameters are ok right now. Any thoughts on what it could be?