Caring for a Goldfish Tank With Algae

Peering through murky, algae-ridden water in your fish tank to try and spot your goldfish is far from ideal. Excess algae can result from the water not being changed often enough or from overfeeding your fish, both of which ultimately provide algae with the nutrients it needs to thrive. Keep in mind that a little bit of algae in the tank can be healthy for your fish, since they eat it and it serves as a digestive aid, so you don't need to eliminate it entirely.

  1. Change the Water

    • Clean, clear water will make you and your fish happy.

      When algae is growing in the water of your fish tank, it means that the water contains a high level of dissolved fish waste, which supports the growth of algae. To eliminate this problem and starve algae of nutrients, you should change some of the water each day until the water is clear again. Do not change too much water at once, as that can be a shock to your fish. Start out with changing about 20 percent of the water daily until you see clear water with no algae. After that, change about 20 percent of the water twice a week to maintain the algae-free environment.

    Cut Back on Light

    • Fish tanks that are placed in areas without direct sunlight tend to stay algae free.

      A tank or fishbowl that gets a lot of light can encourage algae growth, as algae needs light to survive. Move your tank or fishbowl away from sunny windows. Or, cover the side of your tank with foil and keep the light in the tank turned off when possible.

    Introduce Algae-eating Fish

    • Some fish eat algae, such as Plecostomus Catfish and Siamese Algae Eaters. These are both good aquarium fish and will eat some of the algae in a tank. But they will usually not eat all the algae in an aquarium and won't filter out the algae that makes the water green. They are nice additions to any aquarium, but do not count on them alone to solve your algae problems.

    Don't Overfeed

    • Do not overfeed your goldfish.

      If you overfeed your goldfish, you could be encouraging excessive algae growth. Algae loves phosphate, and overfed fish lead to increased phosphate levels in the water. If there is excessive algae in your tank, cut back feeding to once a day.

      Feed your fish what they can eat within a couple of minutes. If your fish doesn't eat all of its food in that amount of time, or there is food left on the bottom of the tank, you are overfeeding it.