2 T5s is a lot of light over a ten gallon. WPG rule doesn't work for T5s and they can cause algae in shallow tanks like ten gallons. I am guessing this is going to be the root of your algae issue and not a nitrate lvl of 40.
Consider dropping a post over in lighting for advice from Hoppy.
In the meantime I would really consider lifting the light a foot, pulling a bulb, throwing in a bunch of floaters. Anything to tone down the light a bit.