Well how long has the tank been set up, what are your water results in ammonia,nitrite,nitrate,and ph, how many fish and which type, how many gallons is the tank, if you are cycling it called a bacterial bloom.
have u added anything recently like gravel, medication or water conditioner? what size is the tank and how long has it been setup? how often do u do water changes?
its been quite a long while scence i have started i have 7 black mollys 6 baby black mollys and 5 neon fish the test from the water are
nitrate : 100
nitrous : 0
gh : 16 0/d ( dont know what that stands for )
hardness : 3 0/d
ph : 7.6
Your nitrate is very high is the reading the same in your tap water. most people around here suggest a reading of 40ppm at the highest but the lower the better. you could do more water changes to bring it down. what is the size of the tank and how often is the water changed?
Its most likely a bacterial bloom, regular water changes with dechlorinator(although don't take out more than 60% of water a day) will help sort the tank out, make sure there is enough oxygen in the water by adjusting the strength of the filter current if your can, how long exactly has the tank been set up and what is the temp in the tank?