How do I stock my new fishpond?

Buying fish for your pond requires a lot of planning to avoid a high mortality rate. Care for fish does not just mean providing food and breeding partners, it also involves maintaining the fishes’ health and protecting them from predators. You also need to be aware of the potential effect fish can have on the local fauna and flora.

It is essential to first determine how many fish and of what size, your pond will comfortably accommodate before going out to buy any. To find out how many fish you can safely stock your pond with, you need to measure the length and width of the pond in centimetres (or inches). Multiply one by the other and divide by 120 (48). This will give you a rough guide as to the total number of centimetres (inches) of fish you can keep in your pond (excluding the tail). Another way of doing the calculation is to allow 60sq cm of surface for every 1 cm of fish (equivalent to 24 sq. inches per inch of fish).  Since fish grow and breed, it is best to start off with around one-third of the theoretical maximum number.  For example, a 1.8 x 1.2m (6ft x 4ft) pond will support 360cm (144ins) of fish, equivalent to 36 fish averaging 10cm (4ins) in length, but, in practice, you should have about 12 fish. In theory, therefore, stocking calculations should be based on the eventual size the fish will grow to. You may prefer to stock your fishpond with a mixture of some small specimens which will still grow and some fully grown larger fish so that your fishpond does look too empty when you first stock it. When stocking your fish pond it is also important to ensure that all fish are compatible.

Once you have stocked your pond you then need to ensure an adequate diet, which is crucial for the long-term health and survival of your fish. All fish require the same basic nutrients: proteins, carbohydrates, fats or oils, vitamins and minerals. Modern high-quality commercial foods are palatable enough to be accepted by most fish. Goldfish, for example, will eat floating Koi pellets and sticks, just as readily as Koi fish. However, the dietary requirements of every species should be investigated and specialised foods used as needed. A large, well-planted pond will contain a good stock of natural plant and animal food items supplemented by flying insects and air-borne plant debris. If the fish in an established pond are few, they may get by without additional food. If, however the pond is well stock, regular feeding is essential.

If your pond is maintained efficiently, with adequate plant and fish stocks, an appropriate feeding regime and a suitable water management system, there should always be sufficient trace elements (minerals or inorganic salts) present to meet the needs of both fish and plants. If you suspect a deficiency, you may add supplements to the fishes’ food, but these should not be relied on long-term as a substitute for a properly balanced diet.

There are a variety of fish available to choose from according to their suitability for large, medium or small – sized ponds:

Fish for large ponds

A large pond is defined as one that holds more than 6825 litres/1500gal of water. The following fish are suitable

Koi and Carp
Giants among pond fish, Koi and other carp can grow to 1 meter (3.3 feet) or more in length and so are only really suited to large, well filtered ponds, without much in the way of ornamental planting, given their habit of pulling up vegetation. Some forms of Koi are highly valuable – running into thousands of pounds, so the security of your pond also needs to be kept in mind. Koi ponds are usually laid out with steep slopes to prevent cats from splashing these ornamental fish out of the pond.

Koi fish require more oxygen than e.g. goldfish. For this reason a Koi pond should be positioned away from overhanging trees to prevent leaves or conifer needles falling into it. Rotting leaves and plant parts consume oxygen thus stealing it from the fish. Feed Koi fish sparingly as uneaten food pollutes the water and supports algae growth.

Fish for the medium size pond

Goldfish
The goldfish remains as popular a choice as ever and generally does well in both larger and small ponds. Its oxygen demands and need for space are low compared to other species. Gloriously multicoloured shubunkins are a goldfish variant. They have black spots on top of a bluish and orange-blotched basic colour. Goldfish routinely grow to 15cm or more and sometimes even double that.

Orfe and Rudd
Many pond-keepers have a particular fondness for the golden orfe, an active fish which spends most of its time near the surface, which makes them easily spotted – though this also means that some form of protection from cats and passing herons is probably a good idea. A gregarious species, they prefer to swim in shoals, so for them to thrive they need to be kept in groups of at least half-a-dozen, but since they can grow to 30cm or more, they need a fair bit of space. However, rudd, which only grow to about half that size, make a good alternative for the smaller pond, being very similar in their habits.

Tenches
Tench are excellent “pond cleaners” since they spend most of their time at the muddy bottom of ponds scavenging for food. The advantage of stocking these fish in your pond is that food left uneaten by the other fish is not left to rot. Aquatic snails are their favourite food. They grow to 25 – 30cm.

Once you get your fish home, float their unopened plastic bag in the pond for half-an-hour or so, so that they gradually reach the same temperature, then open the bag and let pond water enter. This will allow the fish to become accustomed to the pond water – its chemistry will be different. After another few minutes, you can safely release the fish.

Then all that remains is to enjoy your new arrivals!
 

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