help question

[golden69_ca]

i have a 28 gal jbj tank and i am battleing an issue of what i think is some kinda photo algee because when the tank turns on in the morning it is nice and clear and within 4 hours the alge starts to come out and cover the rocks and coral and glass the alge is a browny purple color and looks kinda slimy . was thinking of adding a uv power head has any one experianced this and found that a uv power head fixed the problem . i have done tater changes to no avail all my water paramiters are good . thanks