My fish tank water is cloudy and green. How do I make it clear again?

The green you see is algae. These like nutrition-rich water and lots of light. So you are probably feeding your fish too much and they are not eating all the food. Also there may be too much day light reaching the tank. I suggest you cover your tank in such a way that most of the day light is removed. Fed your fish sparsely. That means, only feed what they can and will eat within one minute. Get some algae-eating fish like a small pleco. Also change about 1/3 to 1/2 of your tank water to remove some of the algae floating in the water.

This can be due to micro bubbles from the filter. This will typically resolve in a few days. If the filter outflow creates a large amount of turbulence, try decreasing the flow rate. Another cause can be a bacterial bloom. This is a common occurrence after a water change and is caused by elevated ammonia levels or large amounts of organic matter in the tank. Either can feed bacteria and promote overgrowth. Check the filter media and rinse it, with tank water not tap water, if necessary. Check the water chemistry using a home test kit or by submitting a water sample for testing. The local Petco may do this for free or for a small fee. Ammonia levels, ideally, should be 0 ppm. Perform a partial water change if necessary. Use only conditioned water that is temperature matched to prevent stress or shock. Condition the water before pouring it into the tank. Remove any dead or dying plants, limit lighting, monitor water temp and don't overfeed. This will decrease the chance of a bloom occurring due to excess organic matter. Luckily, bacterial blooms are not harmful to fish. They can be frustrating, but they do clear up eventually.

Thanks for reaching out. You need to determine why it is cloudy before you can treat. Test for pH, ammonia, nitrites and nitrates. Exam the filters and clean if necessary. Some fish stores will let you bring in water samples to test. Good luck.

The cloudiness can be due to elevated ammonia or nitrite levels or algae blooms. If the tank was previously cycled, the water change may have disrupted the nitrogen cycle resulting in cloudy water. Check the water temperature and chemistry. It is okay to cycle a tank with a turtle in it. They are hardier than fish and can withstand the elevated ammonia and nitrites until the tank chemistry "settles" down.

Goldfish are surface breathers so seeing them up at the top is not unusual. They are also very dirty fish, so I recommend getting a small pump for aeration and doing a partial water change. There is usually a period of cloudy water after establishing a new fish tank until the bacterial balance is established and stabilized in the tank. I also recommend getting a siphon--type tank cleaner so you can use it to clean the gravel as you remove some of the water. It acts as a vacuum to pull out all the fish poo that settles to the bottom, and the water you remove from the tank is a great thing to water any plants you have with, as it also fertilizes them. Remove no more than half of the tank's water and replace it with clean fresh water that has had the correct amount of water conditioner for the volume you're adding.

Check the water chemistry using a home test kit or submit a water sample for testing. The local Petco may do this for free or for a small fee. Aim for an absence (0 ppm) of ammonia and nitrites with nitrates at 20ppm or less. Perform partial water changes to stabilize chemistry and/or to improve water quality. Rinse the filter media in tank water, not tap water, and replace it. Use only conditioned water that is temperature matched to prevent stress or shock. To limit algae growth, maintain pristine water quality via filtration and regular water changes. If possible, turn up filter flow to keep water moving. If this stresses the fish though, do not do it. Do not overfeed and remove any uneaten food promptly. Limit lighting to 8 hours daily and closely monitor water temperature as well. All these can promote algae overgrowth.

I would recommend checking your water quality first to evaluate your ammonia, nitrite, and nitrate levels. With new aquarium set ups, it is common to have issues with water quality as your bacterial populations are getting established. I am not sure if you have fish in your tank already or not, but if you do, please monitor them closely for signs of distress, as this can occur with elevated ammonia and nitrites. Signs to look for would be swimming very fast (hyperexcited state) and trying to jump out of the tank. I hope that gives you a place to start, and good luck!