If you look at your bulb's it should say on them, also is it a one bulb fixture or are there multiple?
As for as the water changes and algae goes you NEED to change your water more often. I recommend changing atleast 25% a week but if that's not possible change 50% every two weeks. The less often you change your water the higher your nitrates get. The higher your nitrates get the more nutrients the algae has to grow and spread!
How long do you have your light's on per day?