My tank is just under a year old, recently water got cloudy for an unknown reason and I brushed it off and just did a water change. Next day water was vibrant green. I did another water change a couple days later but it just keeps getting greener and greener. I thought it would go away but now I cant even see the rock work or corals and I only have an 11g. I never expected this because I have never had this problem in all the months keeping this tank, and I don't know how to get rid of it. I've seen a-lot of posts saying to get a UV sterilizer, but I have a HOB filter so it wouldn't work. Please someone help.