weve Survived the Ich. now the plocostumus is aggressive.

Question
I have a 20 gallon tank. three fish. 1 run of the mill goldfish. 8inches. 1 fantail goldfish 2inches. 1 plocostumus 3inches.
since christmas we've been dealing with tail and fin rot on the two goldfish. they've finally recovered. But in the process my pleco has formed some strange habits. At the worst of the tail rot my big goldfish was dragging his tail on the floor of the tank. the pleco took to sucking on his tail. I thought it was strange and at first the gold fish didn't seem to mind. It didn't take long for him to be bothered by it though. A few days after I first saw the pleco sucking on his tail I came home from work to find my gold fish with spots of broken blood vessels all over his tail,lower fins, and sides. I suspected the pleco was attacking him. this happened on and off for a couple weeks. then the wounds stopped appearing on the big goldfish. The tail rot cleared up . And I thought all was back to normal.
Then last night I saw the pleco attacking both the gold fish . They both seemed really nervous and aggitated. I was scared that he would really hurt the little one. so I pulled him out of the tank and have him In a five gallon bowl for now. I'm confused about his behavior. every thing I've read  tells me that plocostumus are passive fish. I've wondered if he doesn't have enough places to hide in the tank and so he's defending himself . Or is he just blood thirsty?
Do you think it's smart for me to reintroduce the pleco into  the tank? Should I get him some kind of cave if I do?
Any advice would be grand.

Answer
Hi Kelsey,
  What are you feeding the plecostomus?   He needs food. Clearly he is desperately hungry. The best thing to get for him are algae wafers.

 It is a mistake to think that he can survive eating algae off the glass. Some stores will say that, they are incredibly wrong!
A plecostomus needs to be fed just like every other fish unless you have a huge amount of algae growing in your tank.

-- Ron
  rcoleman@cichlidresearch.com
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