Pests in the Aquarium

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Pests are usually found more in the ponds than in tanks; however it is not impossible. Some pests only pose a relatively harmless threat, while others can be rather dangerous to your beloved fish.

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Fish Leeches

These worm-like parasites attach themselves to the skin of the fish and suck with discs that they have at each end of their bodies. The eggs are laid on water plants and this is usually how they are introduced into the tank.

More information on leeches can be read here

Hydra

This is a fresh water creature that consists of a hollow tube like body that has between 4-10 tentacles surrounding a mouth at one end. There are several species, varying in color from white to green and brown. These pests can be introduced into an aquarium by live foods or on plants. In the wild they are found on the undersides of stones or floating leaves. They normally eat small aquatic crustaceans and worms, but the fishkeeper is alarmed due to their ability to paralyze and trap baby fish. It can be eliminated by using a copper treatment,or a 0.3 percent salt solution. Removing the fish and raising the water's temp to 108 degrees F. for a few hours is also effective. Their is also modern anti-parasite treatments available.

Ostarcods

These are small bean shaped organisms. They are entirely harmless. They may be brought in with live foods, plants, or even through water supply. They live in an opaque shell that may be whitish yellow to brown or sometimes green in color. They are 1-3 mm long. The most obvious protrusions from the shell are two antennae and a pair of slender legs, which are withdrawn rapidly if danger threatens. They feed mainly on decaying matter. They provide a someone useful function. Some fish will eat them, and unless they become an unsightly problem, there is not a need to remove them!

Planarians

These are free-living flatworms. They feed on algae and small creatures. They can reach up to 1 1/2 inches in length depending on the species. They are grayish white to brown and black. Planarians are of interest to aquarium keepers because they can be introduced in plants and establish themselves in the sand. They are normally seen at night, where they are seen scouring the walls of the tank for food. They are harmless to adult fish but do pose a risk for eggs in a breeding tank. Planarians can be quite difficult to eliminate. Hanging a piece of fresh meat or liver in the corner of the tank can be successful. You can then remove the meat along with all the worms attached to it. There are parasite medications available to remove these pests as well.

Snails

Many kinds of snails perform a useful function in the aquarium as they eat algae. Most snails feed on rotting vegetation, and leftover food. There are some disadvantages to snails; The Wandering Snail produces a poisonous substance that may cause convulsions in fish. The snail also has an appetite for fish spawn. You should remove them from tanks in which you are using for breeding fish. There are different types of medications available to rid your tank of snails if you should decide to do so! Goldfish will sometimes make a meal out of a snail by sucking it from its shell!

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Snails- Snail faqs by George Booth.