Problems with algae

[bb1clownfish]

There is algae growing out of control in my 55 gallon tank. There is green film on the top of the water and on the sides that returns soon after I clean it. I checked my water levels and they are fine except the nitrate is elevated to ~20. Could that be the problem. If not, I need to know how to fix it. I'm open to suggestions.
Thank you

 

[mie]

What type of lights do you use, and how long are they on for? What type of water do you use? Is the tank by a window?

 

[bb1clownfish]

I use T-5 800 watt lights, the tank is in the basement and has a small window (not much light) above it and I use RO water

 

[mie]

Holy cow 800 watts in a 55! how long do you leave them on for?

 

[bb1clownfish]

Oops, it's 400 watts. Type-o. I leave them on from 1100am to 900pm.

 

[mie]

What are your phosphate readings? Do you have anything to help eat some of the alage?

 

[bb1clownfish]

I do have a reef pack to help eat the algae. ~ 40 hermit crabs, 20 snails, five emerald crabs and a coral banded shrimp. I don't have the equiptment to check the phosphate level. That very well could be my problem. I will let you know once I get something to find out the phosphate levels. Thank you for your help.