Goldfish + algae eater = ???

[brianna021]

I have a pearlscale about 5inchs and a 20 gallon tank with a very strong filter for a 30 gallon.
Recently I have been having problems with algae in my tank I have to scrub it every other day and even when I do scrub it there is still a green color on the glass. The lights are on for 7 hours every day so its not very long and I have this issue.
I have been thinking about adding an algae eater and was wondering if my aquarium is too small for one, what type I can get, will it harm my pearlscale, etc.
I also have algae wafers to feed it if it somehow is able to eat all the algae in my tank.
Thanks in advance:)

[Trillianne]

Have you considered a snail? That may be a good option for your tank size.