using algae eater in a malawi tank?

[claycritters]

I'm still dealing with algae issues despite keeping my lighting to 5-6 hours a day and not overfeeding (4-minute feeding sessions). I've got 8 blue johani cichlids in my 55-gallon tank, and I'm wondering if there are any fish that can help control the algae growth. High phosphates are supposed to contribute to algae growth, but I've never come across a test kit for that - haven't really looked, to be honest.