Sounds like too much sunlight. Try either moving the tank out of the sun or sheilding it from the sun. If you are using an aquarium light on the tank cut the hours you have the light on way back.

There is a condition in aquariums known as "green water", and it's caused by nuisance algae that grows fast enough to turn the water green. Maybe that's what's going on in your tank. I know it's frustrating and you want results sooner rather than later, but only bad things happen quickly in aquariums. (On the other hand, not all bad things happen fast; some occur so gradually that you just don't see the problems developing. Sounds like life in general, huh? ) Maybe you won't get an immediate effect from water changes, but don't stop. Water quality in your tank needs to stay as high as possible. That means, among other things, frequent water changes of smaller amounts, like 5 -10% every 3rd day, or maybe every other day. It's up to you, and there's no hard and fast rule. Try not to use tap water. Municiple water supplies are usually high in phosphates, and those, along with light and air, keep algae fat and happy, or at least colorful and content. Occasionally, I'll see an article or read a posting from someone who swears by a large water change, less often, like 50% every 2 weeks. I've forgotten the reasoning, but it usually makes sense at the time. I still like the smaller/more frequent approach, though. Everything else aside, why make your little pals live in polluted water? Ask yourself which of those 2 scenarios would sound and feel healthier if you lived in a closed space. Instead of water exchange, envision air change and replacement. Overfeeding your fish is easy, but it's bad for water quality. Some flake fish food is really high in phosphates, plus, if the fish don't eat it all, it simply lays around the floor of the tank and rots. It gets eaten, but by bacteria, not fish. That produces ammonia, which is deadly to fish. More bacteria turn ammonia into a lesser evil, nitrites. More bacteria to the rescue and soon you get nitrates from the nitrites. Nitrates may be the least harmful of the three, but they're still harmful and undesirable. When algae's present, nitrates are going to show up at the party, too. If you do tend to overfeed, you have a lot of company. Hard to say no, especially when they swim up to the side, stare you down, flap and waggle their little fins, then waggle faster when they see food. I have a Koran Angelfish who waggles every time he eyes a Kit Kat bar in my hand. It's unbelievable. Besides regular fish food, he enjoys green beans, spinach, and the occasional broccoli crown. Enjoys? My bad. He's like a hog at the trough, sometimes. Turning down such a personable little guy is difficult, but do-able. Be strong. Just say no. Even though he and the other fish try to get every morsel, they miss a few sometimes. Vacuuming the substrate helps, but the fish sure don't like it much. The chaos and upheaval stresses them out, so in general, it's better to avoid overfeeding in the first place. Please don't read that as anti-vacuuming, BTW. It's more of a "minimize the number of reasons for vacuuming" and "less stress means happier and healthier fish." statement. Check your mechanical filter material to make certain it's clean and clog free. The water flows around a full filter, since it can't go thru, and the flow pulls loosely trapped dirt and gunk (like uneaten, decaying food) out of the filter and washes it back into your tank. These algae are single-celled, aka microscopic. If a tank has enough tiny algae to affect the overall water color, that seems like enough algae to give the fish some serious competition for the aquarium's resources. Oxygen, for example. To that end, make sure you keep the tank well aerated. Always aerate the water used for water changes. It's really important. A couple of airstones can't cause enough turbulence on the water surface for really good gas exchange, and that's what aeration involves. If you're near the ocean, the next time you go to the beach, look at the waves crashing against rocks. I think all the white foam and air bubbles just beneath the surface must be the results of aeration. How's your lighting? Algae needs light to grow. Last year, while researching hair algae, I read that no light in the tank for 3 days, helps. Won't hurt the fish. Maybe your electric bill goes down. Granted, not by much, but still. Better down than up. Hope some of this helps your tank. Algae is usually a very tough problem for any tank and its owner, but you're smarter and more resourceful - no doubt about it. Good luck.!

Hello; Algae like other plants need food to grow. If the water has a high Nitrate level from a high fish load, over feeding, or infrequent maintenance algae will flurish. Reduce the lighting and change water more often to reduce the Nitrate level. OFM

hi i had the same problem .. everyone i spoke to kept telling me to much light or over feeding which in fact was neither i checked my pump and found that the circulation of the water was'nt what it was when i bought the tank so i put a new pump in the change was within 24 hours and the fish started to swim more actively with the current of the water so maybe it could help you

MY WATER HAS BEEN GREEN FOR ABOUT SIX WEEKS. I HAVE TRIED WATER CHANGES, FEEDING LESS, KEEPING LIGHT OUT, AND GETTING ALGAE EATERS: ALL THINGS RECOMMENDED BY PEOPLE ONLINE. NONE OF THESE THINGS WORKED. I FIGURED IT WAS AN ALGAE PROBLEM AS EVERYONE WAS STATING. I FINALLY WENT TO THE FISH STORE AND BOUGHT SOMETHING CALLED ALGAEFIX. I PUT DOSAGE OF 12 DROPS PER 10 GALLONS OF WATER. I COULDN'T BELIEVE WITHIN AN HOUR WATER WAS MUCH CLEARER. WITHIN 3 DAYS AND ONE MORE DOSAGE THE THIRD DAY MY WATER IS CRYSTAL CLEAR. MY RECOMMEND GOING TO STORE AND SPENDING ONLY A FEW DOLLARS TO GET THIS STUFF. I HAVE HAD FISHTANKS OFF AND ON FOR TWENTY YEARS AND HAVEN'T HAD A PROBLEM THIS BAD BEFORE, SO I AM NOT A COMPLETE AMATUER.

Hi! I had the same problem and i found taking 1/3 of the water out every other day and we added alegy remover and now it's crystal clear. Thank you. I hope this helps.