Loaches (Weatherfish/Dojos), Family Cobitidae, in Ornamental Ponds

Several species of loaches are employed as scavengers in outdoor ornamental pools around the world. I myself have seen them in several places in Japan and China. Most commonly used are the Common, Misgurnus anguillicaudatus (Cantor) and Spotted, Cobitis taenia (Linnaeus) Dojos or Weatherfishes. A brief comment regarding these fishes second monikers. They are often utilized as "living barometers" on the strength of their increased activity at the approach of changing weather. These fishes are pressure-sensitive, swimming about more if it's about to rain for instance.

The Common Dojo/Weatherfish is drab to light brown naturally, though there are "Golden" Dojos (xanthistic varieties, not albinos) that are human-produced. This species attains a maximum length of about twelve inches. The Spotted Dojo or Weatherfish is less tolerant to temperature change and range; preferring the 50-60's F. and only reaches a natural length of six inches. Both are excellent scavengers for biological ponds. In a stable system that doesn't change thermally much in the course of a day they can exist comfortably in quite warm (tolerable to koi/nishikigoi and goldfish) to near freezing.

These loaches will not hassle pool fishes or plants, except for eggs and fry and take care of large quantities of algae, fish droppings, and excess food. Also unlike snails, they are virtually disease free. What's more, they're reasonably inexpensive.

About one per hundred gallons is sufficient, along with other means (circulation, particulate filtration, partial water changes, live plants, shading, proper feeding'¦) to keep a pond naturally clean.

Bibliography/Further Reading:

http://www.loaches.com (Species Index)

Boggs, Sallie. 1995. Gold Weatherfish. Is this the ideal aquarium fish? AFM 6/95.

Glass, Spencer. 2000. The Weather Loach. FAMA 2/00.

Okamoto, Kikuo. 1922. Secondary sexual characters in the Loach Misgurnus anquillicaudatus Cantor. The Philippine Journal of Science v. 19, No. 6, pp 723-727. 

Palicka, Jiri. 1996. The Spined Loach, Cobitis taenia. TFH 12/96.

Wischnath, Lothar. 1991. Coldwater Loaches- Remarkable aquarium fishes. TFH 12/91.

 Loach with lumps  - 03/12/2006 Dear Crew, <Chris> I have a weather-loach in a 3-foot indoor tank, with two other goldfish. The loach is quite young (I think), about 4 to 5 inches long and I bought him/her last year. <Neat animals> Over the past six months or so, the loach has developed "bulges" in the abdominal area. There are two; one towards the front "third" of the body, and the other to the rear, just in front of the anal cavity. The bulges are visible on both sides of the fish. The loach appears healthy, however, and is active. I cannot find any information about swollen abdomens in loaches; <Really? http://wetwebmedia.com/FWSubWebIndex/loachdisfaqs.htm on WWM> one thought I had was, is this a female with eggs? <Possibly> but having never been sure whether my loach is Lawrence or Laura, I can't decide. Up until last Christmas, there was a second loach in the tank; very old (22 years+) <Wowzah!> and again no idea whether it was a Larry or Lucy. Ideas welcomed, please. I tried to take photos but no luck at present. Chris (UK). <Don't know the precise cause/effect here, but have seen similar conditions in Misgurnis... as you state, doesn't seem to affect their health. Bob Fenner>