New Aquarium -- Advice Needed :-)

[72Super]

Hello Everyone,
Well I kinda "fell" into a 48 Gallon aquarium...some friends of mine were cleaning out their basement and asked if I wanted it..."sure, why not..."
Anyway, I've had water in it for about 2 weeks now, with about 1.5 inches of gravel, some imitation plants, a pirate ship and some column ruins. I'm running an AquaClear 70 with foam, Zeo-Carb, and BioMax and the temperature is set to 84F/30C. Last week I added three black marble angelfish, and they have been doing very well. It took them about three days to get totally comfortable with their new home. Today I decided to add a common pleco, and suddenly I'm noticing some "hostility/bullying" between the angels. Is this because of the new tank mate? The pleco has been keeping to himself since I added him, so I thought it odd that the angels would get nippy...my other theory was that they were just hungry, as I noticed the hostilities start just before feeding time, but it continued after they ate...
Hopefully it's nothing to worry about, but any advice here would be much appreciated.