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


  5. Judy

    Im new to keeping fish and am wondering how long I should let the water sit before adding my fish. It’s town water, 65litre pond.
    How many fish can I initially expect to add… small goldfish at this stage!

    1. Andrew

      Hi Judy. You should wait for min 72 hours before adding fish to a new pond to allow the pH to balance out. However, 65 litres is a very small pond and is, in my opinion, too small for any number of fish. If you would like to keep fish safely I would strongly advise you to consider a larger pond. Sorry to be the bearer of bad news! Andrew

  6. Cristina Prieto

    Hi m building a oval shaped pond( round edges) its 10ft by 6ft by 3ft and it calculates to 5000litres i wanted to know how many fully grow koi i could keep in that volume of water. Also does anyone know were to buy good size quality koi that arent made expensive?

  7. Dave B

    i have an oval concrete pond in a bowl shape it is 2.7m x 2.4m and 36cm deep.
    as this is not very deep what sort of fish would be best suited?


    1. Andrew

      Hi Dave

      I think 36cm deep is too shallow to keep any fish safely as the water will be prone to temperature fluctuations, it will heat quickly in Summer and freeze quickly in winter. I would be much more inclined to use as a wildlife pond. Sorry, that probably wasn’t the opinion you were looking for! Andrew

  8. Kelly Mendoza

    Hi My daughter is desperate for a fish for her birthday (she’s 6) and my husband is dead seat against having any “wildlife” in the house. I’m looking into pond options but wanted some advice on the best outdoor raised pond – we don’t want loads of fish just somewhere that we can keep them safely where they can thrive but also be very low maintenance. Can you help? Thanks

    1. Andrew

      Hi Kelly. We can supply a timber raised pond which will be low maintenance, I would either go for a 1.2 x 1.2 or 1.2 x 1.8 with the larger one being preferable. The height would need to be min 26.5 inches high. I would also avoid putting the smaller option in full sun all day, it will be better in partial shade. I hope this helps. Andrew

  9. Sarah Elford


    I have an old bathtub that we are thinking of using as a pond – using a liner as I don’t want the plug to decay at some point in the future and cause a leak. It will be 50cm deep and about 175 lt. I planned it to be a wildlife pond, but my children want fish.

    Will this pond size be adequate for fish to live happily and safely? If so which fish types?

    Thank you,


  10. Richard Daubney

    I am looking into using a fibreglass bath as a wildlife pond.

    Is a bath to small for goldfish? Would electric be necessary for a pump/ fountain?

    1. Andrew

      Hi Rickard. I would expect a fibreglass bath will be too small for fish. If you want to maintain clear water in the pond you will need an electric pump and filter.

  11. Regina Sherman

    I am having the same problem as Rod Smith’s submission of 8/19/2019.I can not get any fish to live in my recently enlarged fish pond that was enlarged 8 weeks ago. My water hyacinths have what looks like root rot and its leaves are mushy and all my water lettuce has died.My original 4 large gold fish from old pond died when returned to the new pond and subsequent fish have also died. They would come to the top gasping but I have a waterfall with a filter, an uv light and to air stones in my 650 gallon pond. I also have a sun sail in place to block the sun. I took my water to a local fish store which cked my ph and ammonia levels and were within normal limits. No ammonia and ph 7.5 My nitrates and nitrites were negative and my kh is btw 80-120 per dip sticks. I have added bacteria also,my water is very clear. I don’t now what else to do. Please help. Thanks Regina

  12. Libda

    We have a new pond and added fish today, however we had problems with snails eating our Lobelia Cardinal plants. Thought about put cooper tape that you use for pots around the bottom of the plant to deter but as it sits in shallow water could this harm our new fish?

  13. Rick Peterson

    Regina…Where is your uv light? Are you killing off the beneficial bacteria? They usually live in the filtration system…Something is not right…if you have fish you should have nitrogen cycle going…Ammonia -> Nitrites -> Nitrates -> Nitrogen…without bacteria your fish will die…be careful with store bought bacteria…most of this is ground bacteria and will die off as they can’t survive in an aquatic system. One way to kick start a system is to add cheap feeder fish…your not worried that they are going to die…they are there to start the Nitrogen cycle so that you can get a healthy bacteria colony…Also for plants you need to get CO2 in the water…you might look to adding a fermentation container that adds CO2 using yeast and sugar…

  14. Bonnie bernita Magill

    If you fill your pond with tap water remove the fish to a bucket for a couple of days this will the chlorine in the tap water to evaporate the chlorine takes the protective mucus of the fish and makes them prone to all sorts of bugs

  15. Mat Bones

    Hi Andrew,

    We inherited a pond with our new house, it was in a bad state so we’ve fully emptied and relined this year, added a pump (4500 litres/hour but regulated to about half that) to drop the water into a stone bed / waterfall and some plants. The pond measures 3.66m x 2.13m x 0.61m (max depth) so about 4000 litres in my opinion. I’ve also added a small net of barley and the water has been crystal clear since we did the work about 6 months ago. I was fairly happy to leave it for wildlife but was wondering whether you think I could add a small number of small goldfish (2 or 3) and not risk having the pond lose its balance? I’d prefer to not have to introduce any filter system and hence keep maintenance low but would like to see even just a couple of fish to brighten it up.


    1. Andrew

      Hi Mat. The problem with adding fish is they start small but will get bigger and will eventually knock your pond out of balance. personally I would be included to leave it for the volume of water you have and the fact that you would prefer not to install extra filtration. Andrew

  16. Roger

    Hi, we have a new pond, it’s quite shallow (45 cm depth) with 3000 liters of volume. We would like to keep fish in it. Which fish would you advise?

  17. Ann

    Hi, we have 460 litres pond, 45 cm deep at the deepest, but it’s not filled to the top. We got 4 Goldfish but forgot to check if the pond was big enough! Too late now, but will the fish have any chance to survive in it?

  18. Becca

    Hello Andrew,
    I’ve have my goldfish for about 5/6 years now and I made some mistakes along the way (I kept her in a rather small tank as that’s what I was told I could do – I was 13 when I got her) but last June I came to my senses and put her in a 100 gallon pond with three other buddies (one has since passed as a result of a cat attack) then seem to be doing well, I don’t have a filter though, I have a pump that circulates the water but that’s about it – it rains a lot where I am so the water is almost always clear and I have a few plants in there so I didn’t really see the need in a filter – my question would be do I need one? If so is there one you can recommend? I’m fairly new to this and don’t know many others into the hobby. Also, I’d like to add two new members to the pond in the summer (so I would have 5 fish total) is this okay for the size of pond that I have? One of my fish also seems to be a bit plump (and has been since around August so I didn’t think it was a health issue) though I’ve only recently I’ve noticed it has been swimming a little weirdly – no problems with mobility etc. Just a little wobbly? Could you give any advice on this? Sorry for the abundance of questions I just saw you replied to a lot of people and would appreciate the help! Thank you 🙂

  19. V Hart

    I have a structure that I’m thinking of putting a pond in. The size I’ve seen which I’ve seen is 55& a half long 32 and a half wide and 12” deep any suggestions please it’s all the space I have

    1. Andrew

      Hi Viv, I’d suggest using it as a wildlife pond as it wouldn’t be deep enough for fish to survive very long. The water would heat up very quickly in summer and freeze quickly in winter. I’m sorry, it’s probably not the answer you were hoping for!

  20. Tracy Turner

    I have a 250L pond with a pump/filter and a few marginal plants. I’m using tap safe and adding bacteria to help improve the water condition. I lost 2 shebunkins and have either 1 or 2 tench left (small ones) and a few pond snails. I am cleaning the filter every other day but the water continues to be cloudy/muddy looking. Am I missing something important for improving the water quality?

  21. J


    I’ve recently bought a 500L 95L x 95W x 70H pond.

    I am looking to add 4-8 single tail goldfish – it is mostly shade with sunny casts throughout the day. What are your thoughts ?

    Also – what are your thoughts on minnows and other smaller Shoaling fish to go along with these. Understood you would want them larger than the goldfish’s mouth, and how do you suppose they would cope being outdoors? Are there any other smaller recommendations?

    Many thanks.

    1. Andrew

      Hi Joe, sorry for the delay in replying. I’m not an expert in this area but I have read that minnows can quickly overpoulate a pond with goldfish. Also, keep in mind that the goldfish can grow to 10-12″ in length so while 4-8 may fit nicely in the pond at first they will struggle with space later on. Hope this helps

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