Choosing and introducing fish to your pond

Selecting and introducing fish is one of the most rewarding parts of owning a pond.There are many different types to choose from, with varieties to suit every type of pond. However, if you are to keep fish successfully, it is important to select the correct ones for your pond. This will avoid potential problems and ensure that your pond remains well balanced and your fish stay healthy.

Selecting Fish
When selecting which fish to have in your pond, there are a few points to keep in mind:

• Swimming space: Different fish grow to different sizes, with some getting much larger than others. It is therefore important to consider how much space your fish will have once fully grown.A few smaller fish, with plenty of swimming space, will look and behave far more naturally than a large fish squashed into a small pond.Always check information labels to see how large the fish grows before you buy it.

• Depth: Just as different fish prefer different pond sizes, they also prefer different depths.The minimum depth for keeping the majority of fish is 45cm (18in), whilst larger fish, such as koi and other large carp, require at least 90cm (3ft).

Plants: If your pond is heavily planted, then it is probably best to avoid koi and other large carp, as they tend to uproot plants. Such ponds are best stocked with smaller, less boisterous species.

• Filtration: The number and type of fish you can keep is governed by how well filtered the pond is (see the ‘Essential Pond Equipment’ leaflet for more information).A pond without a filtration system may be able to support a few smaller species, but a filter system is essential if you want a reasonably well stocked pond. Most filters will state how many fish they can support, but a good rule of thumb is to allow 25cm of fish per m2 (1in per ft2) of surface area. In ponds with mature filters, you may be able to increase this to 50 – 75cm per m2 (2 – 3in per ft2).

Taking time to consider the suitability of your pond for the fish you want to keep will help maintain a well balanced environment.Always ask for advice if you are unsure about a particular species.

Buying and Introducing Fish
Most water gardening and pond outlets will begin stocking coldwater fish in the spring, and continue to sell them through to early autumn. This is the best time of the year to purchase pond fish, as it avoids the coldest months when the fish are dormant.

When buying fish, always follow the advice of whoever serves you. It is tempting to buy all of the fish at once, in an attempt to populate an empty pond. However, this will lead to problems, as the filter will not be able to cope with the sudden increase in waste levels produced by the fish. Instead, you should stock the pond slowly, adding just a few fish at a time and waiting at least a week or two between each addition. Ideally, you should test the water quality with test kits, such as those in the TetraPond range, before adding fish, as this will tell you if the filter is ready for the extra fish load (see the ‘Essential Pond Equipment’ and ‘Keeping a Healthy and Balanced Environment’ leaflets for more information).

Once you have selected your fish, they will be bagged up for you, ready to be taken home. During transportation you should keep the bag in the dark, to reduce the stress that the fish will be experiencing.Although fish can survive for some time in properly packaged bags, you should always get them home as quickly as possible.

Once at home, place the bag into the pond, leaving it tied up so that it floats. Allow about twenty minutes for the temperature to equalise with that of the pond, and then open the bag and release the fish slowly.

In the days after adding new fish, keep a close eye on them and be prepared to do the odd partial water change should the filter initially not be able to cope with the increased levels of waste. If you do need to do a partial water change, always use tap water that has been treated with a water conditioner, such as TetraPond WaterSafe.

Following this procedure should ensure that any new fish settle quickly and safely into their new environment.

Types of Fish
There are many different species and varieties of fish available for ponds, the following is just a selection:

• Goldfish: The most popular coldwater fish, the goldfish is reasonably hardy and ideal for most types of pond. In most situations, goldfish will grow to around 15 – 20cm (6 – 8in), although they are capable of reaching 30cm (12in) or more, given the right environment. There are a number of different varieties of goldfish available, with popular types including the comet, with its elongated tail, and the sarassa comet, which is red and white with a long tail. Shubunkins are also a variety of goldfish.The more extreme breeds of goldfish, often collectively termed “fancy” goldfish, are less suited to ponds as they do not survive winter temperatures particularly well. Goldfish will often breed in ponds, laying eggs amongst fine-leaved aquatic plants.All the babies are dark brown to start with, with many turning gold and orange within the first few years of their life.

• Shubunkins: A variety of goldfish, but incredibly popular in their own right, shubunkins have all the same characteristics as goldfish, but are generally multicoloured. They are often marked as either “London” shubunkins (with short fins) or “Bristol” shubunkins (with long fins). Like common goldfish, they may also breed in the pond.

• Orfe: Most commonly available as Golden orfe, a blue variety is also sometimes seen.They are a popular and very active pond fish, spending much of their time at the surface.As they prefer to shoal, especially when young, you should ideally have a group of 4 – 6 fish to keep them happy. Orfe can grow large, easily reaching 25 – 35cm (10 – 14in) in even fairly small ponds, and in some cases getting much bigger.They also require well-oxygenated water, and do best in ponds with good filtration systems.Therefore, they are not suited to small ponds.

• Koi: Growing to 75cm (30in) and over, koi are only suited to large ponds with very good filtration systems. They tend to dig up plants and be quite boisterous, and are thus not suited to carefully planted ponds.There are different qualities of koi offered for sale, with the best coming from Japan.The most highly prized of these fish can often fetch many thousands of pounds, and are regularly entered into special koi shows.

• Common Carp: The same species as koi, but not requiring the same level of water quality. Common carp may be seen for sale in various forms, including the “mirror carp”, with its large, reflective scales, and the “leather carp”, which has no, or very few, scales. The true “common carp” is fully scaled. Common carp need the same care and conditions as koi.

• Tench: Preferring to spend their time on the bottom of the pond, tench have earned the reputation of being pond cleaners. However, they merely search for food items in the substrate, and so do not bring any such benefit to the pond.They are, however, an interesting and impressive addition to the pond. Growing to around 25 – 30cm (10 – 12in) in most cases, they are suited to medium to large ponds, with a reasonable level of filtration.

• Sterlets: A more recent addition to the list of available species, sterlets are large, primitive fish, which are popular because of their friendly nature. It is not unusual for them to spend their time poking their noses out of the water, and they quickly become tame enough to hand feed. However, they are a very large and require excellent water conditions, and are therefore only suited to the largest ponds, with the best filtration systems. They are particularly sensitive to low oxygen levels. They also require a pond that is free from blanketweed, as their rigid bodies can quickly become tangled in it. They are therefore not suitable for less experienced pond owners.

• Rudd: Available in either a golden or “silver” (natural) form, rudd are active, surface dwelling fish, which are ideally suited to small to medium sized ponds. They typically grow to 12 – 15cm (5 – 6in) in most situations,although may get larger given enough space.They prefer to be kept in small shoals of 4 – 6 fish, and make good substitutes where space limitations do not permit the keeping of golden orfe.

• Sticklebacks: With their small adult size, and fascinating behaviour, sticklebacks make interesting additions to the pond.They are especially useful for small wildlife ponds, where filtration and space may be limited.

Other species are available from time to time, and it is important to ask for advice before making a purchase. Although some species are native to the British Isles, it is important not to remove fish from the wild for ponds. This is because wild fish pose a significant disease risk, and their removal and translocation is illegal in most cases. Likewise, under no circumstances should you introduce unwanted pond fish into the wild.

Careful selection and introduction of new fish will ensure that they settle in quickly to their new home, and remain healthy and happy.

If your animal is in distress and needs emergency first aid, you must get in touch with a veterinary surgeon in your local area.