agreeded, Take a sample of water to a LFS and have them do a Phosphate and a Silicate test, these are usally the 2 hidden cause for Algea, unless you are over feeding,
What are your feeding habbits?
For now, Cut down to 1 feeding every other day and do 5% water changes every day..
What you may want to do is do like 5 gallon water changes and in the 5 gallon bucket becouse you are using the Tap water, use a condioner.. as well run a powerhead in it and use some Phosphate remover,