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What to do if your fish tank keeps turning green

If you have been noticing that your tank water keeps turning green even after several major changes, then you can take a look at this troubleshooting article from Aquarium Blueprints to see how you can potentially fix this issue.

1. If your tank water keeps turning green, then it is most likely due to algae.

In order to prevent algae from overtaking your tank, we suggest adding live plants. By doing so, the plants should be able to complete against the algae and, therefore, prevent the water from turning into a green color.

In our tanks, we used Java Fern and Java Moss, both of which can grow with no direct lighting. We also dip the roots of Pothos, which will also consume the same nutrients as algae.

By using these live plants, we are able to prevent our tank water from going green as well as any other algae from growing.

2. You should also watch the nitrate levels in your tank water. Ideally, you want the concentration for this compound to be below 40 ppm for most species in the aquarium hobby. For more fragile species, you should target under 20 ppm.

High nitrate levels will most likely result in more nutrients for algae, which will obviously lead to your tank water turning green.

If doing water changes did not stop your aquarium water from turning green, then we recommend using adding a filter media such as Biohome Ultimate or Seachem Matrix as these are designed to lower nitrates. Once you get these medias fully cycled, they should help lower the nitrate levels significantly.

Of course, adding live plants should help as well for keeping nitrates in check.

3. Make sure that you aren’t overfeeding your fish. Most species will only eat for a few minutes.

If you see any uneaten portions once your fish has stopped eating after several minutes, then we suggest that you remove them from the aquarium. Otherwise, the food will end up adding a lot of excess nutrients to the tank, resulting in green water.

4. There is a possibility that your tank is getting too much lighting.

If you are using a dedicated light fixture, then you can try turning it off more often. You fish most likely don’t require bright lights anyway.

If you have plants that need bright lights, then you can add more the same plants in the tank so that they can out-compete the algae that is causing your water to constantly go green.

Furthermore, try to avoid putting your tank in an area that gets sunlight as the natural lighting may be enough to cause an algae bloom. Ideally, you should consider placing the aquarium in a dark room if you are having green water issues. If that is not possible, then you should avoid putting the tank near a window that gets sunlight.