i have a commen pleco, about 7 inches, yesterday i bought a smaller albino pleco, its about 3.5 to 4 inches. well my lager pleco has started to pick on the new pleco and everything else in the tank. they are both in a 55 gallon tank, i bought the new pleco cuz my first one became real lazy, it never moved and wasnt doing a good job keeping the tank clean. why is it that after i introduced a new pleco it became more active and some what aggressive.