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The hydra is only dangerous to very little fish. It is a low type of life, a polyp, that devours fish up to about 3/16 -in. long, and also daphnia.

It has from 3 to seven tentacles spreading from the mouth in a star-like formation, to which the thin elongated body is attached. The actual shape isn’t the exact same in all specimens. They differ widely, making it nearly impossible to describe them with out going into volumes of detail.

It attacks by waiting for a fish or daphnia to pass near sufficient to be caught by the tentacles.

It is then drawn into the mouth to be digested – undigested portions being returned via the mouth. It is not uncommon for a single hydra to have daphnia held by every tentacle waiting their turn to be devoured.

They multiply themselves by budding and division, and given great conditions propagation is rapid.

You are able to get rid of this pest by removing all your fish and bringing the temperature of the water up to 105°F. This is rather an inconvenient technique, and you might prefer to add one teaspoonful of household ammonia to every five gallons of water.

Permit this to stand for two hours after which a complete change of water should be made in the aquarium. The ammonia won’t harm the plants, but fish should be removed.

Flat worms are generally between 1/8 to 3/16 -in. long, and coloured a pale grey, comparable to the body of a garden snail. They could be seen crawling on the glass of the aquarium.

Flat worms aren’t enemies in the true sense of the word, but they’re undesirable. They feed on microscopic organisms, and if placed in clear water will soon perish via lack of food. They could be trapped on a piece of raw meat.

You suspend the meat by a piece of cotton in the aquarium. The meat should be guarded to stop the fish eating it. Should you begin the treatment in the evening you’ll find next morning that there are fiat worms crawling over the meat, which you are able to then remove. Continue this treatment until the trouble is cleared up.

The water tiger is far more risky than the dragon-fly larva. It is the larval type of the big cruel water beetle (Dytiscus), and a lot much more likely to be included with live food as it is a totally free swimmer.

There are a number of species, but from the aquarist’s viewpoint the following holds true of them all. Water tiger larvae are tough to distinguish when little and mixed with daphnia.

Their technique of attack is various from the dragon-fly larvae, which are content to lie in wait. The water tiger will really chase a victim and sink its two hollow mandibles into it, via which it sucks sufficient blood to kill. It then goes off after an additional victim.

The maximum size is 2 inch, and at that stage they’re simple to detect, but you should never permit them to reach such maturity in the aquarium. When they’re only 1/4 inch in length they can mingle with young fry, and will eventually kill them all unless they’re discovered.

The only real precaution is vigilance. Fortunately, some big fish will eat them, particularly cichlids.

It is possible when collecting daphnia to include a couple of dragon-fly larvae in the net. Regrettably, any strainer that lets daphnia via will also pass the little larvae.

There are numerous species, the ringed club dragon-fly (Cordulegaster annulatus) and also the giant dragon-fly (Aeschna grandis), are two of the very best recognized, but they can all be considered under one heading. Their method of attack would be to lie and wait until a fish comes within striking distance, then rapidly extend the mask which fastens tightly on to the fish.

The mask is the organ carrying the mouth and pincers which could be thrust forward at will. The pincers hold the victim whilst the fish is eaten into. Propulsion is by means of a stream of water violently squirted from the body, even though some species get along by wriggling the tail like an oar.

The life of these larvae lasts about a year. The larva then becomes like a squat beetle, at which stage it leaves the water to turn out to be a dragon-fly.

They’re especially dangerous to young fry, and also the only prevention would be to maintain a close scrutiny on live foods.