Look into this thread with a disclaimer that it may affect your livestock. You also need to find out what's causing the algae and make sure you make the appropriate changes whether or not you go ahead with more drastic algae treatments. Your problem may be too much light for the amount of CO2. This can be adjusted by either reducing intensity or time the light is on. You can reduce intensity by raising the lights or placing window screen under the lights. Pressurized CO2 should help but you have to be ready for more frequent pruning and adequate fert dosing.