Raised Timber Ponds

Fish for Small Garden Ponds

Koi carp in holding tank

As you know the Quickcrop research bureau never sleeps. Our aim is provide you with the best products for your garden but also to back them up with plenty of useful information. If there is a meeting of relevant experts that is where you will find us, gently probing seasoned minds for choice nuggets of first hand information. It was therefore no surprise to find a small Quickcrop delegation (myself and my son) at the All England Koi Carp Show in Kent last weekend.

I went to the show to find out how suitable koi carp are for smaller ponds and to learn more about filtration and keeping fish healthy. We offer a range of timber raised ponds which are generous by raised pond standards (the largest is 2677 litres) but would be considered small for keeping large fish.

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You might be surprised how big carp get (I was) with many easily reaching 30-40 cm, it is only when you see them up close that you realise just how much space they need. If you want a long term Koi carp pond you should aim for a volume of 5500 litres as a minumum. Smaller volumes are fine as a starter pond but won’t be able to accommodate the fish as they grow.

Koi feeding in a garden pond

A Koi pond should also be at least 120 cm (4ft) deep to allow large fish to feed. Unlike goldfish, koi have their mouths facing downwards (they are bottom feeders) while we feed them by adding food to the surface. The fish need to keep their head high to take in food so hold themselves vertically in the water, if they don’t have sufficient depth of water they will be unable to do this comfortably.

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You should be aware that Koi also produce a lot of waste which needs a complex drum filtration system to keep the water healthy. Unless you want to clean your filters every day these modern systems start at around €1000 for basic set up so not for the faint hearted. Koi have also been intensively inter bred over many years making them relatively delicate, they will need to be protected from temperature fluctuations and monitored closely for pests or disease.

Obviously I don’t want to put you off keeping koi as it looks like a wonderful hobby but from what I have learned you need to be prepared for what it entails. I think many people think koi are the only large ornamental fish for an outdoor pond without realising what other options there are. The point is Koi Carp are the top end of the fish scale (ha ha) and are more suitable for experienced fish keepers. There are many other very attractive yet much easier fish to maintain, especially in smaller ponds.

Sarasa comet goldfish

Goldfish, Comets and Shubunkins
Koi and goldfish are both species of carp but the smaller goldfish varieties are descended from the Prussian carp while the koi is an intensively bred version of the common carp. The Prussian carp descendants are more suitable for smaller ponds because of their size (adult size 25cm).

Keeping smaller fish does not mean you have to compromise on colour or pattern. Goldfish have been bred in a variety of sizes and shapes including the common goldfish, the long tailed comet and the intricately patterned shubunkins. All the above will grow to 10-12 inches in a well filtered pond and will provide all the beauty and fun of keeping the more demanding koi.

Common goldfish in garden fish pond

Common Goldfish
The common goldfish is one of the hardiest species of domesticated freshwater fish. Goldfish are found in a variety of colours ranging from red, yellow, orange, white, bronze or black. As they are well known as indoor fish they are easy to overlook but are an excellent choice for a small outdoor fish pond. Goldfish variants also have an advantage over koi as they don’t dig out roots of aquatic plants allowing you to add lilies and other ornamental plants to your pond. Koi are the thugs of the water gardening world and will uproot and eat everything in the pond.

As we’ve said goldfish will grow up to 10-12 inches in well filtered water and can live for decades.  I feel sorry for indoor fish in traditional fish bowls as they tend to have a much shorter life due to less than ideal conditions. There is a belief that goldfish grow to the size of their tank but this only partially true. What governs fish size is the concentration of pheromones in the water (a larger volume of water will be more dilute) so the reason immature fish in a fishbowl stay small (and die young) is that their water is not in a healthy state. The same applies to comets, Shubunkins and any other domesticated fish.

Goldfish swimming in garden pond

By the way, the common myth about goldfish only having a 3 second memory is also untrue. Research has shown that their memories are effective over 3 months at least and that they can even be trained to swim through hoops and operate levers. One experiment showed that goldfish learn to push a lever for food but are also smart enough to stop using it if the food supply is stopped after only an hour. These guys are pretty smart!

Goldfish can tolerate low temperatures and will survive frozen over ponds of adequate depth for brief periods provided they have enough oxygen and food. They are primarily herbivores so will prefer a herbivore fish food. Their diet can also be supplemented with pieces of cucumber, broccoli, shelled peas and clippings from certain aquatic plants. High protein feed like worms should be avoided.

Comet goldfish in garden pond

Comet Goldfish
Comets were bred in America and are so called because of their long flowing tails and fins reminiscent of a comet (obviously). Comets sport a range of colours with red, orange, yellow, white and bi-colour versions. They can easily provide level of variety and interest as their larger Koi cousins. If you want a comet with similar markings to a koi the bi-coloured Sarasa comet is the one to go for.

Comets are as hardy as common goldfish and will have the same expected size and lifespan with mature fish reaching 10-12 inches in size.

Shubunkin goldfish small pond

Shubunkin Goldfish
Shubunkins have the same basic shape as the common goldfish and have longer, more flowing fins than the comet. Shubunkins are more likely to be calico coloured with a more speckled pattern. Unlike the comet their body patterns also extend to their fins and tails which look beautiful when they are swimming.

Shubunkins also come in the same range of colours as the comet but can also include a vivid pale blue background. The more blue colouring on the fish the more valuable it will be.

Shubunkins are extremely hardy and will survive in any conditions that a common goldfish can handle. They will grow up to 18 inches long in ideal conditions.

Goldfish for beginners
Under the right conditions, goldfish are a fantastic species of fish to keep. They are hardy, adaptable, long-lived, and are an excellent fish for a novice. Like koi they boast a wide range of colours and patterns to provide years of interest keeping and breeding the fish. Unlike koi goldfish do not require very large ponds or specialised filtering equipment so are also a much more cost effective option.

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  1. Sarah Meldrum

    As a fish keeper as well as a gardener, I would be concerned about the lack of depth and volume in the raised ponds, especially in winter in colder areas of Britain. Regarding fish welfare I would highly recommend anyone considering one to visit https://www.pond-life.me.uk/ – an online community of experts and enthusiasts. Brilliant information, friendly and fast feedback to any questions. Water quality is all!

    1. admin

      Hi Sarah

      Thanks for the info, I have corrected the link to go where I think you intended, let me know if I’m wrong and I can change it. We did a lot of work with a well known fish expert on the ponds Winter suitability and apart from the shallowest ponds we do he didn’t see a problem. We are currently compiling the information into fact sheets which we will display on the pond pages. Can I ask what fish you keep? I would be very interested in hearing some of your experiences.
      Thanks for getting in touch.

  2. nettie

    Hi we have two garden ponds one four foot and one 3foot deep ,in the last snow spell have put a small tube heater in the ponds and i am glad to say all the fish have survived and are now feeding again ,

    1. Andrew

      Hi Nettie
      Thank you for getting in touch. I am glad to hear your fish survived the cold spell and that the tube heater did the job for you. It is great to hear your fish are feeding but remember in cold weather they will need a lot less food as their metabolism is working more slowly. You are also better off using a Winter fish food which is easier to digest like the excellent FishScience cold weather food. I have recently started using FishScience food, it is made from insect meal which is a pond fishes natural diet and so is easier for them to digest than standard fish feeds (which are usually made from fish). I know we sell it and that this is a bit of a plug but I must say I am completely converted. I have also noticed my filter gets less dirty as the fish produce less waste with a food that is in tune with their digestive systems. I’ll stop now! Anyway, here’s a link to the range if you are interested: https://www.quickcrop.co.uk/category/fish-food

    1. Andrew

      Hi, over time the fish will adapt to their surroundings and become less timid. They are social creatures and will benefit from the company of other fish.

  3. Di Walsh

    I have inherited a garden pond with a huge number of fish. They appear to be breeding very successfully. The previous owner did not feed them in the winter but they seem very hungry, they devour any food I give them in minutes should I continue to feed them or follow the previous owners programme? Most of the fish are black with flowing tails some have gold markings, the largest are about 6 inches long, will they all be goldfish?

    1. Andrew

      Hi, the metabolism of a goldfish slows down in the colder winter season and as a result don’t feed as often. Some experts recommend the occasional feed but it does appear that the previous owners’s system is working.


    I am new to fish keeping in a pond, although we did have a very small and I mean small pond at our old address. It didn’t have a pump, well it did, a solar powered one and that eventually gave up. But the one Shubunkin did live for over 12 months until we had to move address, we rent. I then built a larger pond from wooden deck boards it’s 4′ x 2′ and 18″ deep. I got an All in one pump and filter with a UV light from All Pond Solutions and it it lived again for another 12 months, in the meantime we added 2 more Shubunkins and they were very happy, they would come to the surface when we fed them,. But then for some reason the pond was leaking and for the life of me we couldn’t find the leak. So I relined the pond and cleaned the pump and filters plus a new UV bulb and then it all started to go wrong. We lost the 3 fish and we just couldn’t understand why. The water did go very green and mucky very quickly, before I relined the pond it was always clear… So I emptied the pond and started again, this time I left the pond to restart its self. But we are still having problems with the 3 fish we have now got, they are struggling to swim and are very lethargic. I have put some oxygenating weed plant in that we was advised to put in, but that lost most of the little leaves or what ever they were and now it’s just floating on top of the pond looking mushy and horrible. I have also put an air pump in with a large air stone, but unfortunately it’s a solar one and we are not having the best of weather. Also the pond is not in direct sunlight, it is in shade most of the day, so I don’t think it’s that. The small pond we had before at our old address was in the sun for most of the day !!

    It’s one of those that is completely got us confounded….

    Please help if you can, I don’t want to be losing anymore fish so soon….

    Kind Regards


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