Buying Pond Fish

Most pondkeepers have experienced some problems or have heard of other people’s experiences when it comes to stocking a pond with fish.

You have designed, purchased and installed a landscaped garden pond. It has been planted for a couple of weeks, the pump and filter are installed and your back is still aching from the digging and carting of the spoil from the excavation. Now for the finishing touch, a selection of colourful pond fish to inhabit, thrive and perhaps breed in your own aquatic creation.

You have researched how many fish can be stocked in a pond your size and you’ve still got some money left to go out and buy them. Being confronted with tanks full of lively and colourful fish waiting for a new home can be one of the most tempting times for a pond owner. If a few golden rules are not followed then the stocking of the pond with fish can prove to be a costly exercise that could turn your freshly installed slice of aquatic paradise into a watery nightmare.

Golden rules to follow when buying fish for a new pond.

1. Firstly, find a shop offering a good variety and selection of dry goods and fish and particularly someone who puts giving good advice a priority ahead of making a sale.

Before considering buying any additional fish for your pond you should consider whether your pond is ready for its first fish (if a new pond) or is ready for some extra fish if an existing pond.

New pond.

Ideally, before stocking a new pond, it should have been planted and the pump/filter running for at least a week, ideally a fortnight. Raw tapwater and the new pond materials used in its construction create a very hygienic and unnatural environment. Allow the water to ‘age’ and be turned over through a filter for as long as possible before stocking. If possible, ‘seed’ the biological filter and pond with ‘extract of mature filter’ from a friend’s filter.

Existing pond

Are you considering buying fish to replace some recent losses? Be sure that you have established the reason for losing the fish (disease, poor water quality, old age, predation etc) before introducing any replacements or you may experience similar problems again. Ensure a clear two week period between losing any fish through disease and only restock once you are happy with the behaviour and health of the existing stock.

If you are thinking of simply adding to your existing collection then convince yourself that the new additions will not cause the pond to become overstocked. Adding too many fish would tip the balance of a well managed pond increasing the likelihood of water quality and disease problems and reducing growth rates.

2. Stock a new pond gradually.

A garden pond is a living ecosystem where the toxic waste excreted by fish and other organisms in the pond must be broken down by beneficial bacteria in a pond and filter system at the same rate at which it is being produced. It takes time for the bacteria population to react to an increase in waste and if too many fish are added too quickly the waste builds up quicker than it can be broken down, making the pond toxic, which stresses your new purchases leading to their disease or death.

Add fish gradually over a number of weeks, monitoring water quality at every stage (see point 4).

3. Having satisfied that your pond is ready for new fish, select them wisely.

In a new pond it is wise to choose half a dozen of the cheapest fish as a means of testing the water for its suitability for fish. If there is a water quality problem which has not been detected and the fish show signs of stress then you are less likely to suffer great financial loss.

Choose fish that are going to be compatible. Fortunately most pond fish are not aggressive to each other and they all tend to ‘get on’. If a wide variation in size are selected then competition at feeding time may be an issue. Also, it is good to choose smaller fish that grow into the size of the pond rather than buying large fish that may be too large for a pond.

Choose healthy fish.

How can you tell whether a fish is healthy? Some things to look out for.




1. Fish actively swimming in the tank.

Fish hanging at sides of the tank or sulking on the bottom or at the surface. Fish hanging in the water flow.

2. Fish swim towards you in response to your shadow or silhouette.

Fish remain motionless when you walk by the tank.

3. Skin, scales, and fins are clear without blemishes.

Skin, scales and fins are ragged, raised or with off-colour protrusions of tissue from the body.

4. On questioning have the fish been quarantined or held on the premises prior to sale?

Have the fish been put on sale on arrival at the shop? If so, a risk when buying.

5. Water in the tanks is clear, colourless and odourless.

Water has a blue tinge (sign of medication) or milky and a bit ‘whiffy’.

4. Testing water. Healthy water – Healthy fish.

If you are in the process of stocking, returning to a shop for a second or third instalment of fish, it is essential that the filter is maturing and keeping pace with the expanding collection of fish. Most retailers offer a water testing service and will be able to tell you whether it is safe to continue stocking or to wait a week for the filter to catch up.

However, to avoid a wasted journey, you can buy a test kit and test the water yourself at home.

Two essential test kits are pH and nitrite.

pH. Use this to confirm that the water is in the correct range for pondfish. A pH between 7.0 (neutral) and 8.5 is ideal. Watch out for a pH below 7 as acid water conditions must be avoided in a pond.

Nitrite. Nitrite is a toxic by-product of fish waste and its presence is an indication as to whether the bacteria in the filter are breaking down the waste. A nitrite reading is an indication that the water is toxic and the filter is still immature relative to the stocking and no fish should be bought. Wait until the level drops (a few days to a week) and stop feeding to speed up the process. Only stock with a zero nitrite reading.

5. When returning home with your new fish, float them in the bag for 5 minutes. Open the bag and add some of your pond water and after another 5 minutes release the fish into the pond.

Feed sparingly for the first few weeks to allow the filter to keep pace with the waste production and test regularly for nitrite over the first 2 months of stocking. Once you reliably get a zero nitrite reading, it is safe to assume that the filter has matured to the current stocking level and that you’ve come through the riskiest period of fishkeeping.

In conclusion, if there is one golden rule when choosing fish for a new pond it is ‘proceed with caution’. Don’t be afraid to ask questions and by putting the water quality first and the welfare of your fish should follow automatically.

Kill blanketweed and string algae.