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I have 2 mollies 1 common pleco 2 zebra dianos and one rainbow shark I have a 10 gallon I have right now but I also have a 75 gallon tank and I think it's the pleco bioload
That is way too many fish, even if the pleco is a juvienille, he still produces a ton of waste. You need to move the pleco, shark, and mollies to the 75g aquarium, or rehome them. Mollies need 29g of water and a full grown common pleco needs, plus rainbow sharks need 55g aquarium. Please do this ASAP, and until you get them rehomed/moved to the other aquarium, you need to do water changes 2 to 3 times a week, removing about 30% of the water.