Hi everyone I'm new to fish keeping and need some advice pls I started up my new tank 7 weeks ago and was running a internal filter for 5 weeks eveything was fine water levels good but my filter was very loud so I brought a new fluval 206 and was running them together had a good look at tank on Monday and saw that 4 of my fish had popeye treated it stright away with antibiotic .why did this happen my tank is 3 ft I've 4 mollies 4 tetras 1 clown loach 1 krijb 2 gourami. Do I have to strip my tank down. And I've been doing 25% water changes to get my levels back to normal as my nitrats was 100 dxown to 50 now..
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