Plecos are nocturnal yes, but do need a source of light. Most plecos prefer a partial light... so a subdued light is good, either filtered, or low wattage. Wood will make him more comfortable, as well as not looking in on him every ten minutes. Use moonlights or red/blue/green (your choice, I find blue works the best) filters on your lights. Most of these colors cannot be seen well by your fish, and they will think it is night. Keep his diet varied, and full. I use cucumbers, sweet potatoes, potatoes, carrots, algae wafers, blood worms, brine shrimp, beefheart, and occasionally apples, or mangoes, but those are just treats. Provide lots of wood as these guys will eat through a decent amount each year. Give him his own little hiding spot also. Half a pot, foil as mentioned above, the wood itself, ornamental caves, 3D backrounds with caves all make good options.