I have a small 16 gallon tank that seems to like to turn completely green on me in only a couple days. Its just a simple little set up I have in my son's room i use as his night light. I orginally had glo fish in there but that seemed to turn greener faster than if I just stuck to saltwater. Ive had to completely drain, clean, and refill the tank a couple times this year because it got so bad I didnt have much of a choice. During the day the lights stay off. And if nobody is in that bedroom I make sure the room lights are off. My son is only 10 months old so we don't spend much time in his room, so lights are almost always off other than when he goes to bed. I also have black out curtains on his window so no outside light is shining into his room. And for the past month I've had no fish in his tank. I was cycling the tank when I had the ammonia spike happen while I was away and I was only able to save 1 of the 3 fish. Since then I've left the tank empty with just sand and rock in there with the filter running. I do a water change every 2 weeks, but this month I only did it once (about a 35% water change) I can't figure out what makes this tank turn so fast. I just did my 2nd WC for the month and I put a blanket over the tank in hopes that it'll kill off all the algae. Any suggestions would be great! I'm not doing anything fancy on this tank just ur basic hob filter, heater, and fluorescent bulb. Lights are turned on for about 12 hours and that's while he sleeps. During the day the tank and bedroom stays dark. I only want to put 2 or 3 hardy fish in there to entertain him and that's it. Please help!