What type of algae? Brown algae (diatoms)?
There seems to be an epidemic of brown algae/diatoms (really a bacteria). Much of it, imho, is due to an increase in silicates in the supply water and the most likely cause of that is agriculture. With algae, you can treat the source OR you can treat the symptom of the source. Algae and/or diatoms both feed on Phosphates and Silicates. Waste in the tank can be one source, some types of substrates can be a source and silicates in your supply water. You can eliminate silicates in source water with a RO/DI system, you can use products like SeaChem PhosGuard/Net/Bond to pull levels down to a point where a massive bloom doesn't happen. Once you get levels down, they are much easier to maintain at low levels.
Cleaning procedures for existing algae: remove boulders & decorations out of the tank to a utility sink and clean algae off there and not in the tank. Clean glass inside tank and wait a few hours for it to settle and then vacuum. Clean sponges in filters a couple days later. These procedures combined with the SeaChem products will dramatically slow algae growth.
Other tactics include having other plant species that will outcompete algae for those nutrients like Hornwort. Zebra Nerrite snails will do a wonderful job of eating algae, BN Plecos can do a decent job (so I'm told).
When nutrient levels are high enough for an outbreak, you can slow it a little by reducing light levels (especially old fluorescent bulbs which loose spectrum over time). More current in your tank can help. Both of these do not treat the source. The first thing I would do is understand where the problem is coming from: the tap or your maintenance procedures. SeaChem has test kits for Phosphates and Silicates. I suggest you purchase those two kits and test your tank water and your tap water. Report results back here and I will help interpret them.
