philfreenode;4709013; said:put a container of some kind, maybe a pipe, in your tank as a hiding space and then cover the opening and remove it when hes inside
Yes. Absolutely what Phil said. I have moved a very skittish Jack Dempsey this way and it worked great. I used a plastic skull that the fish liked to hide in, then lifted it up with a net underneath.
For your pleco, a piece of PVC pipe with an end cap on one side would work good, or even a plastic 2 liter soda bottle with the bottom cut off (rinsed well of course). Just place the 'hiding spot' in the tank and gently chase pleco into it, then lift out and move to the adjustment bucket.
This should be easy on you and your fish. You won't have to destroy your tank to catch pleco, and pleco won't suffer the stress of being chased relentlessly with a scary net, nor will pleco suffer damage to spines or skin.
Good luck!