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.
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 minimum. Smaller volumes are fine as a starter pond but won't be able to accommodate the fish as they grow.
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.
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 outdoor ponds.
Goldfish, Comets and Shubunkins Koi and goldfish are both species of carp, but the smaller varieties of goldfish 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 pond with a good filtration system, and will provide all the beauty and fun of keeping the more demanding koi.
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. Something to keep in mind if you're ever trying to decide between tank or 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. The optimum water temperature for goldfish is between 65 and 72°F, which is roundabout room temperature. 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 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 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.