Plecostomus can be kept with most any "Community Fish". They should have 10-25% water changes every 1-2 weeks depending how big the tank is, how many fish are in it, what kind of fish are it it, and how dirty the water gets(obviously). They prefer to be in water 72'-82' Fahrenheit. They feed on algae and algae wafers which can be purchased at most local fish stores.
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