Stocking With Fish: Frequently Asked Questions

The idea of being able to enjoy watching a few fish darting around the open water or idling around the lilies on a warm summer’s day has a tremendous appeal and for many people, it’s almost impossible to think about a pond without its fishy inhabitants.

However, whether you’re building a new pond with fish in mind or you’ve inherited an old one from previous owners, adding fish to a garden pond does need to be thought through carefully if they’re going to do well in their new home.

What sort of fish should I choose?

What you choose largely depends on your own taste and how large your pond is – and there’s plenty to consider, including goldfish, shubunkins, koi, tench, rudd and orfe. It’s obviously important to consider the likely final size of the full-grown fish when making your choice; the orfe and koi, for instance, tend to grow too large for smaller garden ponds, though they can do very well given the right environment.

Where’s the best place to get them?

There’s no shortage of places to buy pond fish, from many pet shops, garden centres with aquatic sections and even specialist online stores that will courier your chosen fish over-night to you, in stout bags, in well oxygenated water and contained in stout polystyrene boxes.

Which of these options is the best really comes down to personal preference and what’s available, but on the whole, if you do have a good stockist, there’s not much to beat actually selecting each individual fish for yourself.

How do I know if they’re healthy?

Healthy fish look alert and comfortable in the water, and swim freely with no sign that they are having to fight against either floating to the surface or sinking to the bottom. The dorsal fin should be held upright and all of the fins should look in good condition, the eyes should appear bright and the fish shouldn’t be missing scales or have any obvious signs of damage or disease.

Keep a particular look-out for any white, furry patches that look a bit like cotton wool, which indicates that the fish is suffering from a fungal infection.

How do I know how many to buy?

The number of fish your pond can comfortably support has to do with how much oxygen there is in the water and although obviously depth, oxygenating plants, fountains and waterfalls all affect this, in general it’s the surface area of the pond which makes the most difference.

To work out how many fish you can accommodate, simply multiply the pond’s average length by its average width to calculate the surface area and then apply the general rule of 1 inch of fish per square foot – or 25cm of fish for each square metre.

It’s always better to have slightly too few fish than slightly too many – and remember that in the summer when the fish are more active, the warmer water holds less oxygen than when its colder – so it’s important to resist any temptation to over-stock.

Is there a right time of year to stock my pond?

You can add fish anytime from spring when water has begun to warm up – to at least 10 degrees C (50 degrees F) – through to the late summer.

How soon can I add fish to my new pond?

You need to allow a new pond to ‘age’ for a while before adding fish – so a bit of patience is required. Ideally your pond should have been planted up and the filters and other systems running for at least a fortnight – and ideally more like a month – before you introduce the fish.

Be sure to float the bags they come in for half an hour ahead of releasing them, to allow the water temperatures to match and when you do open the bags, allow some of the pond water to enter for a few minutes before you let the fish go, so they can start to acclimatise to your pond.

There are a few potential pitfalls when it comes to stocking your pond with fish, but with a bit of care and planning it shouldn’t be too hard to avoid them and the end result will be well worth the effort.

Further info

Mixing different fish species in one pond can be problematic as they may display aggressive behaviour towards each other and compete for resources, leading to stress and health issues. It’s important to choose fish species that have similar requirements in terms of water temperature, pH, and oxygen levels. Some species, such as koi, can also outcompete other species for food and should be kept separately.

Feeding your fish should be done in moderation, with only as much food as they can consume in a few minutes. Overfeeding can lead to water quality problems, increased waste, and health issues. Varying their diet with a mix of flake, pellet, and live foods can provide a balanced diet and ensure they receive all the necessary nutrients.

During the winter months, it’s essential to take measures to prevent your pond from freezing over completely. A frozen pond can trap toxic gases and suffocate fish, causing them to die. You can use a pond heater or aerator to keep a small area of the water surface free of ice or even bring your fish indoors to a suitable tank or pond.

Maintaining good water quality is key to preventing disease outbreaks in your fish. Overfeeding and overcrowding can contribute to poor water quality, so it’s important to avoid these practices. Quarantining any new fish for at least two weeks before introducing them to your pond can help prevent the spread of disease. Water treatments and medications can be used to prevent and treat common fish diseases such as parasites, fungal infections, and bacterial infections, but it’s important to follow the instructions carefully to avoid harming your fish or other aquatic life.

Last Modified: April 5, 2023