Stocking with Fish

Adding fish to a pond can add another dimension to your gardening but you have to be careful.

Fish can cause problems in ponds, especially if the pond is overstocked and the water can become cloudy. Fish will eat other wildlife in the pond so if you are installing a wildlife pond it is not advisable to add fish as well. They can also generally make a nuisance of themselves by eating, pulling up and disturbing plants.

Avoid mixing native fish such as sticklebacks with more exotic types like goldfish and carp. Sticklebacks in particular are aggressive and territorial and will harass, damage and even kill bigger fish.

Fish like Koi Carp are very particular about water conditions and usually special filtration is required to keep these sorts of fish.

If you do decide to keep fish in your pond, it is better to purchase them when they are young so that they establish better.

Always acclimatise the fish before putting them in the pond. Usually, they are sold and transported in polythene bags of water. The temperature of the water will be different to the temperature in the pond. To balance this temperature and avoid shocking the fish, float the bag in the pond for an hour or so to balance the temperature before introducing the fish. Do not just tip them in. Gently open the bag and let the fish swim out on their own.

How many fish can I have?

This must be the most common question in any aquatic shop. The answer is simple - for every Square Foot of surface area of pond you can have 2" of fish. This measurement is body length and does not include the tail. If you are buying young fish, remember to allow for their growth. Therefore:

Your pond is 6 foot long by 4 foot wide - 6 x 4 = 24 sq. ft

You can therefore purchase fish that will eventually grow to 48 inches total.

i.e. 8 goldfish (remember, they grow to about 6 inches in length and 6 x 8 inches = 48 inches)

Maintenance

Feed fish daily during the summer months. The more active the fish are the more they will eat, so feeding can be increased to twice a day if needed. Only feed a little at a time and only as much as the fish eat within a few minutes. Excess food will only rot and pollute the water. Towards the winter the fish will be less active so reduce the feeding as needed, stopping altogether as winter arrives and the fish go down to the bottom of the pond.

In hot weather fish can become listless and come to the surface of the water gasping. This is due to the oxygen levels in the water falling. One way of increasing the oxygen is to ensure that the water is moving. If you have a pump installed, make sure that it is running, if you do not have a pump or the fish are still listless, gently spray the water surface with a hosepipe.

Keep the pond free of any leaves and dead or dying plants as these will rot and produce gasses that will reduce the amount of oxygen in the water. To stop leaves blowing into the pond, a net can be fitted over the top.

A net can also help against unwanted visitors that are out to kill the fish. Herons, cats and foxes will kill fish, even dogs have been known to scoop them out.

As winter arrives, keep the oxygen levels up by stopping the surface of the water freezing over completely by fitting a pond heater. If this is not possible, place a floating tennis ball or polystyrene ball in the pond to allow a small amount of air flow.

Suitable Fish for Ponds

Goldfish

Goldfish actually come in many different colours, from white to many shades of orange and combinations of both. They are hardy and easy to look after and rear. They can grow to about 6 inches and will breed freely in good conditions.

Shubunkins

Shubunkins are similar in shape to goldfish but with more transparent scales. They are available in many colours from silver, orange and black with mixtures of all three being common.

Golden Orfe

These are thinner and longer than goldfish and tend to swim a lot faster and tend to swim in a shoal. They are usually a very pale gold colour. They require a little more room than goldfish.

Sarassa Comets

A variation of the goldfish, usually more red in colour.

Koi Carp

These need a lot more care and a lot larger pond than goldfish. They are available in a range of colours and can grow in excess of 12 inches. Although young specimens only cost a few pounds, they can be extremely expensive - enthusiasts can pay in the thousands for them.

Tench

These are sometimes used as pond fish but as they are bottom feeders, they tend to stir up the mud at the bottom of the pond, resulting in cloudy water a lot of the time.