My 40g tank is going through its cycle right now(day 11) and I have rust colored spots on the sand and glass, i think it is diatoms. Look at my 40g thread pics and see if it is similar.
You might want to see if somebody or an LFS will let you borrow one(so you can return it once its eaten all the hair algae) , they tend to starve once all the hair algae is gone