Are my plants eating my fish?

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Sounds ridiculous, but they could be, says Rupert Collins.

I'm sure that everyone will have heard of carnivorous terrestrial plants such as the Venus flytraps, Sundews and Pitchers, but did you know that there are also aquatic versions?

The Bladderworts (Utricularia spp.) are a varied group of aquatic plants, which possess a highly sophisticated mechanism to catch their food.

They have no roots, and the plants tend to creep or float on the surface.

They have traps comprising small bean shaped bladders, and the plant pumps water out of them until they are flat and curved inward under pressure.

Next to the trapdoor, bristles are present, which act as a trigger. If a hapless prey item (e.g. Daphnia) bumps into them, the trapdoor bends enough to break the seal and the walls spring back to their normal shape creating a vacuum, engulfing the prey within one hundredth of a second. The prey is then chemically dissolved and consumed.

But can they eat fish though? While most Utricularia have very small bladders, there are several species with bladders up to 1.2 cm, and they have been reported to eat fry, tadpoles and mosquito larvae.

So, while adult fish are not really at risk, certainly tiny fry could be eaten.

Utricularia are not sold frequently in the trade, but can be ordered from specialist aquarium plant stores, or can sometimes be found as hitchhikers attached amongst floating plants such as Riccia.

Many have quite beautiful flowers, so might develop a following in the planted tank side of the hobby if there is sufficient demand. Some with interesting foliage have even been incorporated into nature aquariums.

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