I have kept a good many pleco's and the personalities range, but currently I have two that are very active all over the tank most of the day, and one that stays hidden until nite or makes an appearance if a good veggie or wafer are offered.
Maybe this is a time to define "active". I am not talking frantic or swimming without feeding. If you have frantic activity, you should start by checking water parameters.
Setup on 11/4/06, 90 gal, 80 degrees, Corallife 65 watt 4 light 6K range on 10 hours a day 2.8 w/gal, Pressurized C02 on pH Auto-Regulator 7.0 25 ppm C02, Rio reactor, 11 degrees hardness, 120 ppm Alkalinity, Fluval 405 Canister...
Balansae, Dwarf Subulata, Tall Subulata, Corkscrew Val, Anubias Petite, Anubias Barteri, Temple Plant, Wisteria, Lobelia small form...
2 - 4" upside down cats, 5 - 3" glass cats, 1 - 4" Chocolate Pleco, 1 - 3" Brisslenose Pleco. 1 - 2" Rubber Nose Pleco, 4 - 2" Otocinclus, 2 - 4" Silver Dollars YIKES, 7 - Rummy Nose Tetra, 8 Neons...
Run 2 airstones at night don't cut off C02 and 8 LED light blue night light.