Remove any winter equipment from your pond. Reinstall your pump, filter, and any water features. Perform a large water change, about 20%. To help reduce stress and illness in your koi, increase pond salinity to .3-.4%. Switch on UV filter to help combat algae blooms. The average cost of a koi fish in the UK can range from £10 to several thousand pounds. This broad price range reflects the diversity in quality, size, and rarity among different varieties of koi. For example, smaller and more common varieties like Kohaku or Sanke can be found at affordable prices starting from around £10 to £50. Butterfly koi are cold-water fish, but too much cold can be deadly to them. Koi fish can handle temperatures between 33 and 90 degrees Fahrenheit. If temperatures in your area ever fall below 33 degrees, a heater can keep your butterfly koi from freezing to death. This is a crucial step in caring for your butterfly koi. Cost: $3.50-4.50. These fish have quite long hooks. They’re also fringed out such as the females and are splayed unless the fish is ill. They rise to the same dimensions because of their Veiltail counterpart (being 1.75″-2.25″) Fun Fact: Also called”Fancy Betta Fish.” Male Deltatail Betta (Normally Blue) Cost: $6.50-$8 Modern examples of koi fish can cost less than $10, but some sell for thousands or more. Ginrin; Price: $80 – $90 Alternate Name: Cyprinus carpio Koi pond cost. A koi pond costs $3,500 to $17,000 on average installed, not including the fish. The cost to build a koi pond depends on the size, depth, features, and whether installed professionally or DIY. Koi pond kits cost $550 to $6,100. Koi pond maintenance costs $600 to $3,000 per year. 12 Rare Koi Fish Varieties 1. Ki Utsuri. Ki Utsuri are a variety of black koi fish with yellow splotches all over their bodies. They are members of the Utsurimono family and are considered among the rarest of koi varieties. Ki Utsuri is basically a yellow variety of utsuri koi which get their distinctive coloring from a recessive gene. How much is a full grown koi worth? Koi fish typically cost around $20-$50 for a healthy koi measuring around 5″ in length. However, prices can range from $5 to well over $10,000 depending on the type and size of koi fish. nK4E.