I also appologize for you brother and think that you keeping his fish is a good cause and while you may be overstocked, you can compensate in some ways as well as possibly look for a bigger tank in the future. I don't really want to say much either because of your situation and all, but if you really want to keep your brother's fish as long as possible, you will need to make sure there is sufficient room for them. If they get crowded, they can become stressed and there is a lot of problems that can quickly follow that. It is such a touchy subject and I hope you can 'hear' the sincerity in my 'voice' when I say all of this.
What I haven't heard anyone say so far though is that while pleco's enjoy the popularity they get from being 'algea eaters' and many people buy them for almost every tank they have or still own, the truth is that they are NOT really all that great at eating algea. In fact, even in a small tank with a very small pleco, every owner should suppliment their diet with things like algea wafers or veggies like cucumber. In fact, plecos are also very well adept at eating any left over food that passes by your other fish and sometimes will actually gravitate towards that type of nutrition. Bottom line for ANY fish is that it will often eat foods that are out of 'character' for it and is the reason behind not putting any fish in a tank that can fit into another fishes' mouth.
Honestly, I am sure people are about to disagree with me here, but if you were just looking to control algea in your tank, a chineese algea eater or a siamese algea eater are much better as far as fish go and snails are also a great addition for algea only purposes. If you are having an algea problem right now, it is most likely (here we go again...) because your tank is overstocked and there are too many nutrients in the water that the algea can live upon. It might help you to just increase your filtration for now to help remove some of these nutrients as well as up the amounts of water you change weekly (with so many big fish, weekly is almost a must in my opinion).
The other bottom line is that plecos are plecos no matter what you feed them or how much you feed them. They are going to make large amounts of wastes and that is unavoidable without completely starving it. I swear to you that if you stop feeding them all of a sudden, you are going to catch one or more of them sucking on the side of another fish because the slime coat is highly nutritous and so long as the fish doesn't die, a renewable natural resource. This is especially probrable if you have large, slow moving fish, which may be somewhat more true about your larger fish who cant really run too far in any direction.
Like I said, I am trying to pass my opinions, ideas, and information in the nicest possible way here and I hope that you do not take any offense to what I said. I feel that the biggest problem with only having written communication to speak through is that you cannot hear 'how' I am saying what I have typed out. I just dont want to see these very precious fish be hurt of otherwise destroyed by what is much more of a myth than a fact about these plecos. If anything, only feed them slightly less or in smaller and smaller increments until they are acclimated to the amount of food that they are given.
To keep the cucumber or zuchini from floating (which I found my pleco is most fond of), get yourself some lead weights that are used to secure live plants to the bottom of a tank. Sorry to disagree here fballguy, but boiling them for 15 to 20 minutes would only result in a bunch of 'goop' right away or in very short order once it is in the tank. I think he may have meant to 'blanche' them or put them in boiling water for 15 to 20 seconds since this will help sanitize the veggies and remove any poisons or preservative agents that were applied at the farm/grocery store. It is a good idea to do that and then throw them quickly into cold ice water to stop them from cooking more. I use the little plant weight idea and it works really well. Some LFS give them to me for free even.
Keep smiling and never give up.
The Pacu seems to like the zuchini.
