Rather that dose the tank I think it would be better to address the causes of the algae.
1) Light - how long are the lights on during the day? If it's more than 8 hours consider reducing it.
2) Nutrients - these can be too high for a couple of reasons
a) Over-feeding - it's easy to over feed our tanks but the excess food will decompose and cause nutrients to be released into the water. Only feed as much as your fish can eat in 2 minutes - no more than twice a day. One day a week do not feed the tank at all - this will make the fish hunt their tank for any left-over food they can find.
b) Water changes - Nitrates and Phosphates will build up in your tank with the normal action of the filter on fish waste. These need to be removed by regular water changes. Increasing the regularity of water change will decrease the nutrients.
c) Filter activity - filters will be reduced in effectiveness if they are not cleaned regularly. Rinse the sponges in a small bowl of tank water to keep them biologically active.
Follow these steps and remove what algae you can by hand and you should be on the way to stopping the problem re-occurring.
You might also consider an algae-eating fish. Without knowing your tank size it's difficult to advise but there are a number out there: Otocinclus, Bristlenose, Plec.
