4 part attack for your problem
1st: On a tank that size you could get by with just a Hang On back skimmer and some powerheads. But you need to lose the canister. Unless you clean it every day it will cause algae.Use a skimmer like the seaclone 100. I have one on my Nano and it work better than the skilter or the prizm.
2nd: Try a phos remover like Polyfilter. It not only grabs the phos from the water it also strips a lot of the metals out the help the algae to grow.
3rd: Stop all flake food, high in ash and phosphates.
4th: Water changes. if you have a ro/di filter do a continous water change routine. 1-2 gal a day. If you dont have one try this. Warning upcoming product plug
Petco sells real Pacific ocean water (filtered) in a 5 gal box for about $9.
If you can afford it, it is unreal how good it makes a tank look. I have been using it in my nano (I change 1 gal mon and thur every week) for the 4 months it has been up. The results are incredible. all of the microlife on the live rocks came alive and the tanks cycled in 4 days.
In my experience those 4 Actions will almost always work to retard and reverse algae.
To prevent future outbreak add sand stirring critters. the black cukumber, or some good sand moving snails will help keep down the problems by cleaning up the waste on the bottom of the tank.