This fierce predator among goldfish is large, often 2 inches or more in length, and sometimes hard to find, for the dull red or olive-brown coloring blends in with surroundings. It also can live under water for long periods, as it submerges with a supply of air bubbles sticking to its body and need not surface until they are exhausted. It is capable of inflicting a bite that causes severe swelling, so exterminate it with care.

A transparent polyp, the hydra is 1/2 inch long when fully extended, a fraction of that when it contracts its body, which it does when disturbed. It anchors itself to something solid and waits for prey. It is a menace only to newly hatched fish, but disastrous among them. The hydra, with a cylindrical body, and with up to a dozen tentacles surrounding a mouth at the free end of the body, stupefies its prey with poison, then draws nourishment from it at leisure. To rid an aquarium of hydra, remove goldfish and snails, and fill with a solution of household ammonia and water, 1 teaspoon to every 5 gallons. Clean and refill the aquarium after two hours.

This pest is ferocious and destructive to a degree out of all proportion to its size, which is seldom more than 11/2 inches long. Sometimes this beetle is solid brownish-black; sometimes it has a narrow border of brownish-yellow.

It is dangerous, for it is as agile as it is ferocious, and successfully attacks goldfish many times its size. It is as much at home under water as on the surface because it submerges with a bubble of air which it holds at the tip of the abdomen, a supply which lasts a long time.

The life cycle is a difficult one to fight, too. Whereas most water beetles lay their eggs on water plants, where the fish eat them, the Predaceous Diving Beetle deposits eggs within the tissues of the plants. The larvae that hatch from them are fish killers, too. <BR><BR> Fortunately, these beetles are easily spotted, even in very large pools. Dip them out as you see them and destroy them.

This is the larva of the Water Scavenger Beetle, and it is as deadly an enemy to goldfish as the Water Tiger. The body is round and plump, often 3 inches long. It stalks, pounces, and sucks blood with the same hunting technique as the Water Tiger.

A couple of aquatic bugs which look a1ike in size, brown color, and shape, range in length between 1/4 and 1/2 inch. Look at the bug carefully if you see one in your pool. If there are two pairs of legs, one pair of which is held out like a pair of oars, you need not bother. It is a Water Boatman, which the fish will eventually catch and eat. If the bug has three pairs of legs, destroy it. It is a Back Swimmer, which attacks snails and small fish and can even bite human beings. A small amount of kerosene added to the water will kill the Back Swimmer when it surfaces to breathe.

This is a bright red, globe-shaped parasite which sometimes attaches itself to goldfish. It is not dangerous but a nuisance