The new filter was what I was afraid of. I don't think you have the proper bacterial colony for those fish. Here's an idea to catch the pleco. Place the picture in the tank overnight and place a blanched cucumber slice in it. Pretty much certain the pleco will go right in.
aahhhh see thats the kind of answer i was looking for. i have chased the thing around the tank several times and all it does is stress me and the other fish out. i will be sure to try this thanks