green water problem?

[KMACAS]

I have one 45 gallon tank it has penguin 330 biowheell power head with filter and a cheap protien skimmer (not the best but it is working O.K. for this tank size<all other skimmers are expecive and for biger tanks).I have 4 x 40W 48" light bulbs they are 50%daylight and 50% actinic blue so they are blue.I checked the Ph NH3/NH4 NO2 NO3 everything is fine. What do you people think the problem is ? is the green water rotifers ? or somthing else?Please only reply if you want to help me out thank you.