A 6 inch pleco is way too big to be in a 10 gallon tank and probably too big for a 30 hex. Is it a common pleco? If so they need at least 75 gallons of tank but most people will tell you they need 125. Enough of the lecturing, I would add a small school of tetras to the tank to help the cycle along. There is nothing wrong with cycling with fish as long as you stay on top of the parameters and maintain them properly.
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