Well, there is no need to keep adding the meaty food if they won't eat it. Like I said, that will not help. If they liked the food particles for whatever reason, you could try instead of feeding them new food to stir up the substrate a bit. This will release a lot of particles, many of which are probably food. I believe plecos are largely nocturnal, so they may be eating the algae stuff. It may be beneficial to add it a little before you turn out the lights, so it won't have dissolved before they are active. Is this a sinking algae pellet? Or like strips of seaweed? If you want to confirm, you might be able to sneak up on the tank a few time at night (if you don't use much/any light) and try to see.
I thought of one other thing you could do with the real wood when you get it: rinse it off well, then put it in the main tank but weigh it down. Whatever you do with the real wood, make sure there is something in there at all times, real or fake, as they like to hide in it and may be stressed out if there is not any.
Regarding tanks, you can probably find a variety of tanks for a good price on Craigslist, assuming price is the main problem. I can't guarantee, since I don't know where you are, but around me there are many.
Something else that occured to me, where did the goldfish come from? Did you add him immediately to the tank with the plecos? Most fish keepers will quarantine new fish in a separate tank for a few weeks to make sure they have no diseases. If the goldfish also came from Walmart or a big box pet store, there is a good chance it had some sort of disease, particularly since it died so quickly. The best place to buy fish is typically an lfs, since they usually obtain better and care better for their stock.
One last thing, do you have a thermometer? What temperature is the tank water? Not likely to cause a big problem, but if the goldfish is no longer there, about 76* F is pretty good for most fish, and the plecos would be more comfortable there.
I found this website on plecos that you might check out:
plecostomus.org. I also like this website for general fish information, including plecos:
SeriouslyFish.com. Go to the knowledge bae on this one, and then the tab siluriformes, the suckermouth armored catfish. Or, you can search pleco, but either way there are a lot of different types. You might just want to check out a few types to get an idea of some general common characteristics.
Brian