Introducing Fish to the Garden Pond
Enlivening the pool with
A garden pool is not complete unless it has a complement of ornamental fish. Even if your main interest is plants, do not neglect this aspect of, for, apart from enlivening the pool with their antics, they are beneficial in controlling aquatic insect life such as mosquito larvae.
There are quite a number of different hardy ornamental fish suitable for the garden pool, but all have similar requirements and comparable stocking rates. The number of fish a pool will hold is a perpetual topic of discussion for which there are no hard and fast rules. However, through experience I have discovered that 15cm length of fish, inclusive of tail, for every 0.093 square metre of water surface, except in the very smallest pools, is the maximum that can be achieved without causing discomfort to the fish. In a newly established pool this ratio is undesirable, for most gardeners like to see their fish grow and also get quite a thrill if they happen to breed. Neither of which is likely to occur in a fully stocked environment.
Initial stocking at about a quarter of the maximum rate will allow the fish to develop naturally. At this juncture it should be noted that all ornamental fish grow in accordance with their surroundings. Thus a small goldfish which has been confined to a round glass bowl for several years will remain the same size, yet once liberated into a garden pool will almost certainly double its size within a season.
Another interesting fact to appreciate is that most fish consistently occupy one level of the water. Thus golden orfe will be found just beneath the surface of the water, goldfish and carp towards the middle zone, and green tench and catfish on the pool floor. Of course, all swim about freely and occupy one another’s territory from time to time, but knowledge of their more usual habits enables a selection to be made so that all three zones are constantly inhabited. Although this should in no way alter the ratio of fish length to surface area.
May I also reinforce here the point that I made previously, that fish must not be introduced to the pool until all the plants are well established.
Choosing your fish
Before venturing amongst the many varieties of ornamental fish that can be introduced to a garden pool, I feel that we ought to get clear what a healthy fish looks like. Healthy stock is of paramount importance whenever fish are introduced. A small diseased goldfish placed in a pool with established, vigorous, healthy specimens will quickly lead to disaster.
All fish that are in good health have stiff erect fins and bright eyes. Smaller sizes, especially, should not have any scales missing as these leave an opening for infection. They do on larger fish as well, but it is almost impossible to find an adult fish that is intact. If an otherwise healthy adult fish has a scale or two missing, dip it in a solution of malachite green before introducing it to the pool. This should go a long way towards preventing fungal disease gaining a hold.
Obviously any fish that are thought to be diseased or suffering from general malaise must be avoided. One or two species develop specific characteristics before their demise. Green tench turn from a lovely greyish olive-green to black and catfish behave similarly. Some carp suffer from a condition known as ‘Big Head’ in which the head seems over-large and the body narrow and pinched. Nobody is certain what causes this, although in some cases it could be fish tuberculosis, but whatever it is, death is swift. Those delightful little dumpy fantails are prone to swim bladder disorders. So any that swim more or less permanently upside-down or in a crazed fashion should be regarded with suspicion.
Although it is not always possible, it is preferable to select your own fish. If this proves impractical, then place your requirements in the hands of a reliable supplier.
Mail order suppliers despatch fish in heavy gauge polythene bags with just sufficient water for them to maintain equilibrium, the remainder of the bag being blown up with oxygen and then placed in a stout cardboard carton. These are then despatched overnight by passenger train. On arrival remove the bag, and without unfastening, allow it to float on the surface of the pool. This enables the temperature of the warmer water within the bag to be equalised with that of the pool. After a short time the fish can be released into their new home. On a very hot day gently tip the fish into the pool without floating the bag, for the stifling effect of the hot sun can be more harmful than putting the fish into icy water.