Problem with algae

[Gaines69]

I work at a school and we have a FOWLR 29 gallon bio cube. It’s been up and going for almost a year. At this time there is one damselfish and a few snails and hermit crabs. ( damselfish has killed everything else). At the beginning of this school year we had a big algae bloom. I think it’s hair algae. Anyway we scrubbed the walls and liceneocks to remove as much as we could. It was gone for about a month and now it’s back. Took in a water sample and have night nitrates and nitrites and no ammonia and water has a green tint to it. Girl at lfs said to do a 20% water change every day for several days and to add more snails. My question is this. Is it better to add snails to eat the algae and do a lot of water changes or add media made to get ride of nitrates/nitrites etc. both the teacher and I have researched the subject but there are conflicting information. Also what lights should we leave on? I read the fluorescent tubes and I have also read LEDs. I know it’s probably be best to do no lights for a while but one light has to be on to have the fan running. I have moved one powerhead to point upward to have movement on the surface of the water and scrubbed everything really well. A new filter cartridge went in today and the sponge material was rinsed ( with tap water). Any suggestions would be most appreciated. I am so confused. Thank you
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[Gaines69]

Why am I not allowed to view the pictures I attached to my post???

 

[ritter6788]