i had a 10 gallon tank that the water kept going green in it an i thought it was over stocked so last week i set up a 36g tank for the fish.(2 red tail sharks"about 2 inches each" 2 glow fish"inch each" 2 tetra "inch each" 1 fancy guppy "1 inch" neon tetra fish "1 inch" and 2 other fish that i forget there names but they are only 2 inches each. and it has been 1 week and its green already. i have 1 17w 8k bulb thats on from 10 am to 10pm. fish tank is next to a window but does not sit directly in front of the window. i have 2 filters ones a aqua tech 30-60g then the others a aqueon and i thinks its good for 30g.