doesnt too much light cause algae? i've been lucky, so havent eexperienced this. i'm sure i've read somewhere on here about a 5 hours on, 5hours off rota or something like that, as the 5 hours on isnt enough to promote algae growth. i'm sure someone can fill in the gaps in my knowledge with the exact timings and help you. basically, less light = less algae! also, can you fit an algae eater in the tank? they'd have a feast! either way, try not to go down the quick fix chemical route as once you start, you'll never get out of it! good luck and keep us posted.
ATM - thought there was a 5 hour in there somewhere and summat to do with time it takes for photosynthesis!!!! i just couldnt recall the full info!! glad you had the answers as that's been buggin me all day!! Carols idea makes even more sense to get on top of it!!
Just wanna quick add something to this post even though it s old. If the tank has any kind of sunlight hitting the it, that can cause a massive algea growth of the green type, if that is the case relocation and a couple day blackout with solve the problem with many water changes. Good algea eaters are also good to help control algea too, less work for you free food for others.
I agree with the rest, light and nutrients are the two factors that promote algae growth. You need to test your water for ammonia, nitrites and nitrates. If your tank is properly cycled it should read 0 ammonia, 0 nitrites and the nitrates are what feed the algae. Water changes if the nitrate is 10 or more will help rob the algae of food. My tank is a bit overcrowded, so I change 50% water every day or every other day. I HIGHLY recommend different algae eaters, you will note most folks keep a pleco, otos, shrimp, or some like snails (watch out here as some can reproduce so fast they are a problem). Some fish like mollies eat algae also. The thing to remember is not to overcrowd your tank by getting lots of new fish. Unless you have a very large tank be sure to get a dwarf pleco if that is what you want. Otos are always a good bet as they don't grow very big, and do a great job of cleaning plants they are happiest in numbers though, so get 3-5. You will most likely need to do a combination of all above to get it under control. Good Luck.