Fishes

No pond or aquarium should be without its complement of snails, for this reason, they are perfect scavengers. They devour decayed  or decaying vegetation which induces bacterial growth and also help to clear the sides of the pond of the green algal growth that so distresses the pond keeper. This greenness, formed by a minute and lowly plant, which increases under sunlight, can be combated only by the humble snail. It is not in the least harmful to the fish, still it looks unsightly. The snail feeds as the winkle does, by passing over these tiny plants and rasping them off with its file like tongue. To be at all effective at least a hundred snails will be required for our pond. The most common snail used for this purpose, in England at any rate, is the Ramshorn Snail, a flat, convoluted animal. A red variety is much sought after for the aquarium, but, as snails are not much in evidence in the pond, the common or garden kind will suffice. Snails collected from a wild pond, or any other creature for that matter, should be quarantined in a small tank for a few days. Snails have the unfortunate habit of harbouring worm-like parasites. The eggs of the snail form an excellent food for the fishes; they are laid in jelly-like masses on the underside of the leaves of water-lilies and other aquatic plants.

Fresh-water whelks also are good scavengers but they are so enthusiastic that they eat plants before they have decayed, moreover they may attain, according to the species, quite a large size, and be more a menace than a benefit to the plants.

During the summer months, with the action of sunlight, the water may, and doubtless will, turn green. This unsightly greenness is caused by the same algal zoospores that stain the sides of the pond, the only difference is they are in a free state.

Green water is also caused by a minute organism called Euglena viridis, one of the Infusoria. It is  roughly oval in shape and has a whip-like appendage by means of which it is driven through the water; the total length of Euglena is about one two hundredths of an inch. Paramceciurn is four times as large as Euglena and is also responsible for a part of the green tint; the body is covered with a number of very fine hairs which serve the same purpose as the flagellum of Euglena. Paramecium is the finest food known for young fishes. In spite of that the fish-keeper likes to see crystal-clear water. There is only one way of achieving this for changing the water itself makes not the slightest difference, it will be just as green in a couple of days and that is by calling on the Fresh water Mussel, otherwise the Swan Mussel, alias Anodonta cygnea. This mollusc may grow to a length of six inches and as it progresses by ploughing its way through the soil, it is apt to uproot the plants, especially those that are not properly established.

In any case the aquarium is no place for the Swan Mussel, for the aquarium one or other of the small and dainty Pisidium or Sph criurn genera are advisable. I do not know of any dealer with any of these tiny mussels on his list but some of the species are quite common in ponds and slow-moving streams, from which they may be collected

This entry was posted on Sunday, March 28th, 2010 at 4:30 am and is filed under Uncategorized. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.