How to Culture Greenwater

Co-authored by Joe Perez

Last Updated: April 29, 2024 References

Greenwater, or phytoplankton, are known by most aquarium hobbyists as good quality small fish fry food, like betta fry. This article will outline some of the ways you can make your own.

Method 1

Method 1 of 2:

Simpler, slower method

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Doing this takes quite a long time for the algae to bloom.^{[2]
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Method 2

Method 2 of 2:

Faster method

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Don't use soap!
You can also add fish micro pellets to help the culture bloom more quickly.
Do this for about 1 minute.
In about a few days, the phytoplankton will grow.

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Question

Even after sieving all the leaves out, it is okay for the green water to have a thick, more green sediment at the bottom and the top to clear up a little and become less green?

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Yes, this is probably common as some of the blended leaves will be in pieces that are too small for a simple filtering material. If you want to filter as much as possible I suggest something like nylon stocking material. It tends to filter better than cheese cloth and you can get it for $1 at a dollar store. I use them as a mechanical filter for my 55gal tank.

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The green water in one of my plastic buckets turned red, why?

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There are many types of algae, blue, green, and the most primitive type are red. I am assuming that somehow red algae spores got into your greenwater culture, and took over.

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I had fish poop from another aquarium I wanted to use for watering the plants, but the water turned green in a few days. Is that green water safe for feeding?

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Yes, it is. You'll get an added benefits from the algae and other microorganisms that are in the green water.

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Tips

Use smooth, thin leaves so they will easily blend in a kitchen blender. Avoid adding hard and thick leaves because they will not emulsify well.

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You will notice quite a lot of algae on the surface of the water- this is phytoplankton. At this time, you may add daphnia culture (water fleas) to the phytoplankton. Your local pet store is a good source of Daphnia. The adult stage of the Daphnia are a great live food for the aquarium.

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Microwave the leaves to kill the plant cells faster.

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Warnings

Do not feed the fresh blended greenwater straight to your fry! Let it sit under the light so the phytoplankton will grow and all of the cells in the leaves died first. Some cells in the leaves are the defense system of the plant and this can kill your fry.

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