HELP! I Cant clean my AIO.

[HighCounryReef]

Ive had my 30 gallon AIO running for about a year and I have stayed current on my weekly maintenance, or so i thought. I have notice alot of hair algae growing in the small compartments separating the sections in the back. Their too small to get a tooth brush and I am out of ideas.

Any ideas?

Its the water box 30.2

 

[Geebs19]

Anyway to make a makeshift cover so it doesnt let light in? No light with starve out the algea. I actually just made one for my 100 gallon tank today and put it on.