What Are Tank Bugs?

Written by dawn colclasure
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What Are Tank Bugs?
A dirty fish tank and excessive food can attract tank bugs. (Photodisc/Photodisc/Getty Images)

No matter what kind of precautions you take, the same kind of bugs that appear in fish ponds have a way of getting into your fish tank. Some bugs will fly into the tank or manage to crawl in. Tank bugs tend to show up if you overfeed fish. Some tank bugs won't hurt fish. Others, such as flatworms, are predatory. They will eat fish eggs and any small fish they can catch. An abundance of tank bugs is usually a sign that the tank is not being kept clean.

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Called flatworms because of their appearance, planarians eat other living or dead invertebrates, as well as decaying organic matter in the tank. They will not, however, eat or harm your fish. Planarians can be white, grey, brown or black. These worms have a regenerative ability; if a part of these worms is cut off, it grows back.


Nematodes are another type of worm that can be found in a fish tank. These worms are thin, long, and they move by squirming back and forth. Unlike planarians, these worms are round. They won't hurt fish; they are often a food source for them.


Copepods, seed shrimp, white lice and daphnia, also known as water fleas, are the types of crustaceans that can thrive inside a fish tank. White lice and daphnia almost look like seahorses except their "belly" is much larger. One type of copepod is the Cyclops, often sold as fish food. The Cyclops is so named because it only has one eye, however this is typical of all copepods, which look like tiny bugs that are less than 2 centimetres long. Seed shrimp look like tiny clams, yet they also have only one eye. Seven tiny legs are found beneath the flattened shell that covers their head and thorax. These crustaceans eat algae, bacteria and micro-organisms. White lice, however, will bite and drink the blood from fish.


Mollusks, or snails, are often found in fish tanks. These snails can be very tiny or larger. One type of snail commonly found in a fish tank are limpets. Limpets are snails that usually have one foot and a large, conical shell. They can get as big as 5 centimetres in diameter.

Insect Larva

Mosquitoes, dragonflies and damselflies often have larvae growing in a fish tank. One other type of insect larvae you'll find in a tank is the bloodworm. They are the larvae of the midge fly. The bloodworm is a food for many fish and reptiles.

Water Scorpions

The water scorpion is a tank bug that can fly in and out of a tank. If you keep water scorpions in the tank, place a mesh covering over the top to keep them from flying out. Water scorpions feed off of insect larva. These bugs can sting, so be careful when handling them.

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