A lot of the time the local non-chain places are a little more concerned about the welfare of the fish they sell. Especially fish stores that don't sell other pets. If they sell sick, unhealthy fish or make bad recommendations they lose business and many small places like that can't afford to lose business. They are often run by hobbyists as well, so there is generally a good level of knowledge at least for the owners. I have a wonderful hobbyist-owned shop in town, where the only employees are the husband and wife owners and sometimes their adult daughter helps out. They know many of their customers by name and remember who keeps what. She lets me know when she is getting new stock in, especially stuff she knows I'm interested in. She even knows where I work, where my boyfriend works, and asks about him whenever I go in without him. They kept my latest tank on hold for a month until we could pay it off, and stayed after closing time to help us load it in the car. There is also a pet store in my old hometown that I visit whenever I'm down there during the daytime because they have a topknotch aquarium section, fresh and salt. Never had a problem with their fish, and I've been known to make the hour long trip to get some fish. If you can find a good local store to take the Pleco I'm sure he will find a good home. Also, I think it would be nice of you to buy your brother a cool looking snail to replace the Pleco as an algae eater. If he is young, that might help him with the idea of taking one of his fish. This is also a good opportunity to teach him about being responsible for his pets and putting the needs of the animals he wants to keep ahead of what he wants to keep. This is, of course assuming a younger brother who still needs to learn these lessons. If you are both young, I'm sure your parents will appreciate you taking the responsibility to care for your pets and for teaching your brother about it.
