How big do Koi get?I've had one for about 8yrs now in a 40 gallon tank and it's now almost 12in long.?

Question

Will it out grow the tank eventually?

Answer 1

It already has outgrown its tank. A fish that is a foot long (and will get bigger) either needs a huge tank (100+ gallons) or a pond. Koi are not really aquarium fish. See if you can find a home for it in a friend's pond. That is your best option weather you like it or not.

Nosoop4u

Answer 2

Average koi reach lengths over 3 feet (45 pounds). if your Koi is 8 years old and only 12" he is stunted. Koi can and do grow 8 inches in their first year and 12-18 in their second.

Your koi even if he is of the smaller variety is seriously on the small end of the scale. You really should move your koi to a larger home. Remember koi can live up to 200 years! (Most however do not that is an exceptional koi with perfect habitat) Average life for koi kept in ponds in North America is around 37 years. (Of course some longer)

What are you feeding your koi? Koi need a balanced diet. When choosing a fish food choose one with high protein (48% or better) and low fat (5% or less)

You can supplement their diet with things like Lettuce, mustard greens, turnip greens, collard greens, spinach, peas, endive, Watersprite, seaweed, cukes, kale, chard, broccoli, lima beans, green beans, etc. and feed aquatic plants (e.g. duckweed, azolla, salvenia, etc) or hair algae daily.

For their Carotenoids which are a family of pigments the fish can't make themselves and are obtained as part of the diet. These pigments result in red, yellow and orange colors. Fish have cells called chromataphores. Those cells convert lutein and carotenes into astaxanthin which is the red pigment.
sources include, brine shrimp, krill, spirulina, marigold flowers, paprika, sweet red peppers, yams, carrots, pumpkin

Watermellons and oranges are also good as well as proteins like chicken (chicken livers) beef (livers and parts) and pork as well as worms and bugs.

At the length he is at now in the small tank he should be fully grown at around 30 inches.

NO he will not out grow the tank but his life is in jeopardy. Koi as well as all fish that have been stunted have a long road ahead of them.

Also, stunting does not mean their interiors continue to grow. If that were the case you would have a beach ball in your tank not a fish. The entire fish gets stunted and doesn't grow properly. This is the problem when trying to bring them out of the stunt and forcing organs to "start" growing again.

Answer 3

If it is already 8 years old and only 12", it probably is too late to save it, in terms of it living a "normal" life, and get much more growth out of it. I have had koi reach that length within two years - in rare instances, even one year (it depends on the food, water temperature, water quality, etc., etc., - even the pattern/color type. The ones that look like wild carp such a sarugoi and chagoi grow faster and bigger, and the more colorful types, especially the utsuris, tend to grow more slowly. Also, females usually grow bigger than males). They generally get most of their growth with the first three years or so, and can easily get to 24-36". They can also easily live to be 20, 30, 40 years or more (there are some annecdotal accounts of them living to 150 years!). Since it is now stunted, growth wise, your will not live that long. Its insides have continued to grow and develop, even though its outsides have not, so it is highly likely that its internal organs are cramped together and somewhat deformed, at least.

At this point, since it has been in the tank for so long, it is not conditioned to living in a pond. It does not have the muscle conditioning, nor is its swim bladder conditioned to swimming in a much bigger area. If you decide to put it in a pond, it is best to let it adapt gradually by putting it into a cage (easy to make with a PVC pipe frame built into a cube/box, with a mesh screen sewed around it, leaving the top open - be sure to keep the open top a couple of inches above the water level to prevent "escape"). This will limit the amount of area (including depth) in which your koi can swim until it builds up the stamina and strength to take on pond life.

If you don't have access to a pond, then I guess just give your koi the best life you can in its current home. If you are able to afford a larger tank for him, it would certainly be better, but if not, just do what you can to continue giving him as good of a quality of life as you are able.

Hope this helps - good luck.

Answer 4

that fish is extremely stunted.
koi can reach well over 3 feet if kept in proper habitats..meaning big ponds(thousands of gallons), not tanks.

stunted means that the fish's body stops growing, but the internal organs contine to grow. this leads to premature death. and not a peaceful and easy death for the fish.


if you want to make your fish comfortable, get the biggest tank you can. 200 gallons or more. and no other fish in the tank, just the one koi. over filter the tank and feed a varied diet. the fish is already stunted if only 12 inches after 8 years.

Answer 5

If you provide your Koi with a larger tank...better yet a pond environment...your Koi will get larger. Just because he is 8 years old, does not mean that his growth is halted. BUT...he will not get any larger in the 40 gallon tank you have now.

You don't mention whether you have any other fish in your tank, besides your Koi...if you do, it may be best to give him a tank all his own. My rule I always follow, is one gallon of water to one inch of fish.

The average size a Koi can get in a large aqaurium or pond is around 18-24" Please note that I said "average." They can also live for 50 years.

Answer 6

It all depends on there environment, water quality and the food they digest. They can grow 30+ inches if given the right parameters and can out live a human. A koi can reach 12 inches in 2 years so yours is small for its age but I guess in your case that is a good thing cause a 30+ koi in a 40 gallon aquarium doesn't make for a good combination. :)

Answer 7

It already has outgrown the tank. Kois get big about 2ft at least.

Answer 8

1) it already is CLOSE to outgrowing the tank and 2) thet CAN grow (in the right enviroment) 30inches plus