It's difficult to say with 100% certainty withouth seeing the entire fish nor know its size or age, but it appears to me you have a "Network" or "King Tiger" or "Scribbled" pleco, more specifically Hypancistrus L66. They have a pretty distinctive pattern so I'm betting that's what he is. If so, he won't get any larger than 5", so as long as he is in a tank of 20 gal minimum size you won't have to worry about him outgrowing your tank. They eat a meaty omnivorous diet, so sinking algae wafers are fine but be sure he gets plenty of high-protein stuff such as sinking shrimp pellets and frozen bloodworms. These type are NOT wood-eating, although he will appreciate hanging out under a nice piece of driftwood. Be sure his water is warm (about 80°) and that there is a good current in the tank (can be achieved by turning your filter flow on high). Like most plecos he is nocturnal but you still may see him often in the daylight if he is comfortable with his surroundings.

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