We have a sump tank which fluctuates normally between 50 to 125 gallon. There are 4 drains from the bell siphons and a bypass of the excess water being pumped back to the FT, all supplying aeration to the tank. We have been using the services of a plecostomus to keep the algae under control. Our second, last plecos has died and now the algae is starting to build up again.
Should we be that concerned about the algae? There is a lot of aeration in the tank for the algae to live on. Or, should we get yet another plecostomus? They are a bit on the pricey side. Donna says we need a smaller fish because they are cheaper.
how much of your algae is exposed to light? Usually you can keep it under control simply by making sure the water is well shaded. When I had a koi pond, I kept some barley straw in the pond which also helped to control it.
If you have media beds, I would say simply block the light out from the fish tank completely for a while till the algae dies, the decomposing algae in the grow beds will give off a similar chemical as the barley straw and will help inhibit future algae blooms.
Surface algae on the sides of a tank is usually not something to worry much about. If the water is turning green to the point where you can't easily see the bottom, that is something to worry about since it can get so thick (pea soup) that it can consume all dissolved oxygen in the tank overnight and kill not only itself but the fish as well and it can cause extreme pH swings between day/night.
So if it is just the walls of the tank turning green, don't upset your self too much. If the water itself is turning green, block out the light to kill it off before your fish are swimming in pea soup.
If you have a local pet store such as PetCo or PetSmart, you can usually adopt fish for $1 from them. I found an 8-10" pleco and got him for a buck. They tend to have many fish for adoption, though they will not market them, you will want to ask in person...