Problems with Goldfish


1 Colour changes

Goldfish tend to change colour. Most change during the first year of life, but others change throughout their lifetimes (which should be at least 10 years). Inexpensive goldfish change in unpredictable ways because their parentage is uncertain and their colour genes represent a random mix.

Expensive “purebred” goldfish should exhibit significantly more predictable changes, achieving similar colouration of their parents as they mature. But be warned: If you purchase young (under a year or so), high-quality goldfish you cannot be certain that the colours you see are the colours you’ll end up with a year later.

Most importantly, colour change in goldfish is not a disease. Treating healthy goldfish with antibiotics is a sure-fire way to kill the animals (and guarantee one final colour change).

The single most important determinant of goldfish colouring is genes. What they inherit from Mom and Dad makes all the difference.

Colour-enhancing foods can accentuate colours that are present, but otherwise subdued, but only to a limited degree. Sometimes dull orange goldfish can be “reddened up” with algae supplements or parboiled vegetables, such as peas. However, a side effect of colour enhancing foods is colour shifting on multicoloured goldfish. White areas on ranchus or sarassas, for example, can turn orange.

The most effective way to enhance existing colours in goldfish — whether it is red in ranchus or black in moors — is to place them in a sunny outdoor pond. The combination of stable water quality, several hours of sunlight, and natural foods — algae, worms, insects, etc. — will bring out colours in your fish like nothing you can imagine.


2 Flotation (buoyancy) problems

If your goldfish tend to bob at the surface like corks (either right side up, or upside down), or bounce around the bottom like blobs of jelly, think “eating disorder.” Commercial goldfish are not “natural” fish. They are bred to look the way they do. Unfortunately, playing around with genes often produces unwanted side effects (mutations can occur in nature, as well, often to the disadvantage of the animal or plant).

Playing around with body mass and shape, in particular, causes problems with flotation. The ability of a fish to stay neutrally buoyant (that is, not have a tendency to float upward or drop downward) involves a careful balance among the internal quantities and locations of body fat and meat, fluids, air and ingested material. Slight deviations from balance mean trouble.

In the real world, fish with buoyancy problems are quickly eaten by predators (or starve to death) and so they have no chance to reproduce and pass on the genetic mistake that created the problem. In the commercial world, such “defective” animals are continually produced — and aquarists buy them. Often, the problem does not appear until the fish has matured and has become a favoured pet.

Ninety-nine percent of goldfish flotation problems are caused by a combination of physiological manipulation and feeding. They are not the result of bacterial or parasite problems and so treatment with fish drugs will not solve the problem.

You cannot repair the physiological quirks, so your only option is food. Feeding a variety of foods, including parboiled peas, duckweed and algae can often correct balance problems caused by dry commercial foods jamming up the fish’s digestive tract. All pelleted or flaked foods should be presoaked before feeding. This prevents the dry foods from absorbing water internally, swelling up and blocking the fish’s digestive tract.

You should change your feeding regimen from one or two large feedings to three or more small feedings. Goldfish do not need to eat large amounts of food. In fact, controlled studies show that underfeeding fish produces the healthiest and most long-lived animals.

Be prepared for the fact that all too often this is a permanent and irreparable condition. You have to decide if the animal is suffering and would not be better off joining the 10 zillion goldfish that prematurely meet their maker each year.


3 Mixing goldfish and tropicals in the same tank


This is a really, really, really bad idea. Goldfish should be held in a separate species tank because they:-

i) have different water quality demands (lower temperatures and more oxygen) than tropicals;

ii) grow much larger than most tropicals, requiring greater feedings, causing them to produce more wastes and thus place larger demands on filtration systems;

iii) need larger tanks than most tropicals; and

iv) are often victimized by more aggressive tropicals.

Life is always more pleasant for goldfish when they have a tank or pond setup just to meet their requirements, and they are not subjected to the indignities of slime-sucking plecos and the like.


4 Using algae eaters in ponds to clear planktonic algae

The short answer is that you shouldn’t. Algae eaters do not eat the algae that turns ponds green and even if they did, they could never, ever come close to eating enough to make any difference in the water transparency.


If your pond water is routinely green and you want it to be more transparent, you have three options. First is heavy planting of aquatic vegetation (or a vegetative filter), second is installing a biological filter, and third is installing a UV sterilizer.

Vegetation or a biological filter will remove ammonia, and to a lesser extent phosphorus, that the algae need to live, from the water. Using vegetation, you will notice near overnight clearing when the plants are growing most rapidly in the spring and during flowering. Some greening returns as plant growth slows in the summer. You can maintain the clearing effect by cutting back plants and forcing them to regrow shoots (but this is not always the most attractive thing to do).

Nitrification filters can also clear the water, but they are not always successful. They seem to be most effective with a moderate fish load in the pond. Combining nitrification and vegetative filtering improves the chances for clearing the algae. A UV sterilizer is always effective — it just zaps the algae.


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