Green water won't go away!

[victor123]

so I have got a 20 gallon turtle tank with one 6 month old razorback musk turtle, for filtration i have got a AllPondSolutions 1000ef canister filter and recently a 700 if AllPondSolution UV sterilizer filter. As you can see i have tried everything from daily water changes, buying a UV sterilizer and reducing light and feeding alot less. The aquarium gets baisically no sunlight. I'd like some tips on why my aquarium hasn't cleared after 3 weeks with the sterilizer. One of my hypotheses is that the water conditioner i use is green, and could possibly stain the water? Anyway, some help would be appreciated!