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Aquarium Duckweed Tips and Tricks

February 26, 2012

Most aquaculturists love  duckweed for its natural beauty and value it as a highly nutritious food source for goldfish, bettas, koi and others.

However, the downsides are that duckweed has a tendency to take advantage of the ammonia in a fish tank and grow TOO fast, clogging filter intakes, and sometimes introducing parasites and snails into an otherwise balanced aquatic system.

You CAN add duckweed to fish aquariums if you are willing to do the following:

1. Disinfect your duckweed if you are concerned about its source. I raise mine outdoors and have not had an opportunity yet to do this, but there are sites that describe how to use a weak solution of bleach or potassium permanganate to kill parasites and snails. (See Aquaculture discussion.)  Always save back a portion of your starter duckweed sample just in case.

2. Once introduced into your aquarium, monitor duckweed growth daily. This means having a fish scoop handy to harvest floating biomass in excess of half the surface area of the water. Give excess to other indoor pets if appropriate, compost,  or immerse duckweed in water and freeze in a dedicated ice-cube tray. When solid, pop out and keep frozen in a plastic baggie for future aquarium fish feedings. Freezer shelf-life is approximately three months.

3. Some folks have had good luck with floating duckweed corrals, either home-made or purchased floating rings or rectangles.  For best results, keep corrals anchored away from filter intakes. If fish are quite active eaters, they may splash duckweed over or under the edge of the corral and you’ll have duckweed on the loose. However, the bulk will be contained and since you’ll be keeping an eye on them anyway, the strays that don’t get eaten can be rounded up easily.

4. To keep duckweed from clogging your filter intake, move opening of intake to 4 inches below water surface and use a bit of cheesecloth as a primary filter over intake. Monitor daily to insure that cheesecloth is free from duckweed accumulation and to allow filters to be effective.

In summary, growing duckweed in with your aquarium fish  is doable and makes for a continual, fresh and healthy snack for your aquarium friends.

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