I would load a small squirt bottle with Hydrogenperoxide and squirt it directly on the algae - don't get carried away but don't be afraid to give it a couple of good squirts. Hydrogenperoxide is indeed poisonous to most fish, but not in the quickly diluted aquarium and it's totally inert in about 24 hours. If you have a whole lot of algae, spray about 6-12 inches long by about 3-6 inches wide every 24 hours until it's all gone. Hydrogenperoxide will also kill plants, but again, not in these small amounts even if the algae is on the plant. The plant will survive and the algae won't. Hydrogenperoxide over the counter is a 3% solution usually. That's what I'm talking about. Do NOT use anything stronger and you'll do fine. It's cheap, fast, easy and can be repeated. I do not know of any fish that will have problems with this approach and bottom dwellers are my passion and they are usually the first ones impacted by things like this. I have not tested it on shrimp or other non-fish animals.
