So I recently bought a used 125 gallon tank. Cleaned it up real nice with zero chemicals. Transferred majority of water from my 55 gallon tank (cycled) and still using the same cycled filter on my 55 so I know I have plenty of beneficial bacteria. I did add a lot more decorations, but dunked them in boiling water to kill any bacteria before adding them. My tank came with a 4 small cichlids. I lost three fish to a fungus and two fish from what I can only assume as aggression issues. My tank recently has become cloudy. Water parameters are near perfect as always with only about 20 nitrates. I do 25% water changes twice a week, and add SeaChem Safe to water when I do them. I just got done from treating the tank for 7 days with API Melafix. None of my other fish have any signs of fungus or fin rot. Am I safe? Or do I need to do more to prevent this from happening again? Tank has African Cichlids and a Pleco in it.