# Goldfish: How big do they get?!?! **URL:** \ **Category:** Factual Questions\ **Created:** [July 16, 2006, 2:42pm UTC](https://boards.straightdope.com/t/goldfish-how-big-do-they-get/364737 "2006-07-16T14:42:47Z")\ **Posts on this page:** 7\ **Page:** 1
**Author:** ![Scruloose](https://avatars.discourse-cdn.com/v4/letter/s/e68b1a/32.png) [@Scruloose](https://boards.straightdope.com/u/Scruloose)\ **Post date:** [July 16, 2006, 2:42pm UTC](https://boards.straightdope.com/t/goldfish-how-big-do-they-get/364737/1 "2006-07-16T14:42:47Z")
A few days ago I was looking down into the water at the entrance to the Chicago river when I saw some pretty big goldfish. They were 12"-15" easy, and bright gold in color - so I’m assuming they were goldfish. A colleague I was with saw them and remarked that goldfish size is usually limited by their tanks or bowls, and when they end up in a large body of water, they get H U G E. :dubious: ( \<— naturally skeptic of all things provided without authoritative citation thanks to the conditioning of the SDMB smiley) OK - so: 1. Is it possible that I saw really big ‘traditional’ goldfish? 2. Is their size limited by the tank or bowl they’re in? 3. Just how big will those suckers get? ---
**Author:** ![Johnny\_L.A](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/johnny_l.a/32/1084_2.png) [@Johnny\_L.A](https://boards.straightdope.com/u/Johnny_L.A)\ **Post date:** [July 16, 2006, 2:57pm UTC](https://boards.straightdope.com/t/goldfish-how-big-do-they-get/364737/2 "2006-07-16T14:57:10Z")
When I was a kid I bought some ‘feeder fish’ for a nickle each, goldfish that were intended to become meals for oscars and whatnot. I had a five-gallon aquarium. Then they moved into a ten-gallon aquarium, and then a 20-gallon one. They grew slightly as they were moved into larger tanks, but not much. Then mom put a fish pond in the back yard. Maybe 300 gallons or so. These nickle-a-piece goldfish grew to about six to eight inches long. And they started breeding. 12" to 15" is a larger goldfish than I’ve ever seen, but based on my experience with my goldfishes it sounds plausible. I’ve heard that goldfish will grow to a size sustainable by their environment. This seems to have happened with mine. No idea what the upper size limit for a goldfish it. ---
**Author:** ![don\_t\_ask](https://avatars.discourse-cdn.com/v4/letter/d/e68b1a/32.png) [@don\_t\_ask](https://boards.straightdope.com/u/don_t_ask)\ **Post date:** [July 16, 2006, 3:04pm UTC](https://boards.straightdope.com/t/goldfish-how-big-do-they-get/364737/3 "2006-07-16T15:04:29Z")
[Here](http://www.guinnessworldrecords.com/content_pages/record.asp?recordid=57554) is the record 18.7" ---
**Author:** ![Surly\_Chick](https://avatars.discourse-cdn.com/v4/letter/s/ec9cab/32.png) [@Surly\_Chick](https://boards.straightdope.com/u/Surly_Chick)\ **Post date:** [July 16, 2006, 3:23pm UTC](https://boards.straightdope.com/t/goldfish-how-big-do-they-get/364737/4 "2006-07-16T15:23:34Z")
> [@Scruloose](#): > > A few days ago I was looking down into the water at the entrance to the Chicago river when I saw some pretty big goldfish. I’ve seen those fish too and they’re enormous. I don’t know if they’re goldfish or what but I once saw one of them eat a new baby duckling! :eek: Well, I assume it at it rather than it just being a malicious drowning. ---
**Author:** ![yabob](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/yabob/32/2821_2.png) [@yabob](https://boards.straightdope.com/u/yabob)\ **Post date:** [July 16, 2006, 3:32pm UTC](https://boards.straightdope.com/t/goldfish-how-big-do-they-get/364737/5 "2006-07-16T15:32:15Z")
They can’t grow indefinitely. There is some point at which “cube/square law” considerations will make the design not work. Even if you provide a habitat the size of Lake Superior, you aren’t going to get a fifty foot goldfish. The Wiki article says: > [@](#): > > It may grow to a maximum length of 23 inches (59 cm) and a maximum weight of 6.6 pounds (3.0 kg), although this is rare; most individual goldfish grow to under half this size. In optimal conditions, goldfish may live more than 20 years (the world record is 49 years); however, most household goldfish generally only live six to eight years. I would guess that the fish in the Chicago River are common carp - related to goldfish, but they get bigger. In fact, here’s a blurb about the “Chicago Carp Classic”: [http://www.carpecarpio.com/chicagocarpclassic2000.html](http://www.carpecarpio.com/chicagocarpclassic2000.html) ---
**Author:** ![yabob](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/yabob/32/2821_2.png) [@yabob](https://boards.straightdope.com/u/yabob)\ **Post date:** [July 16, 2006, 3:42pm UTC](https://boards.straightdope.com/t/goldfish-how-big-do-they-get/364737/6 "2006-07-16T15:42:31Z")
It’s probably also worth noting that people will often confuse koi with goldfish, since the koi may exhibit similar coloration. The koi is an ornamental domesticated version of the common carp, which can grow to 4 feet long. Wiki article on koi: > **[Koi](https://en.wikipedia.org/wiki/Koi)** > > Koi (鯉, English: /ˈkɔɪ/, .mw-parser-output .IPA-label-small{font-size:85%}.mw-parser-output .references .IPA-label-small,.mw-parser-output .infobox .IPA-label-small,.mw-parser-output .navbox .IPA-label-small{font-size:100%}Japanese: \[koꜜi\]), or more specifically nishikigoi (錦鯉, Japanese: \[ɲiɕi̥kiꜜɡoi\], literally "brocaded carp"), are colored varieties of the common carp (Cyprinus carpio) that are kept for decorative purposes in outdoor koi ponds or water gardens. In recent years, there has bee... ---
**Author:** ![running\_coach](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/running_coach/32/15836_2.png) [@running\_coach](https://boards.straightdope.com/u/running_coach)\ **Post date:** [July 16, 2006, 6:53pm UTC](https://boards.straightdope.com/t/goldfish-how-big-do-they-get/364737/7 "2006-07-16T18:53:09Z")
[A Fish Out of Water](http://www.amazon.com/gp/product/0394800230/qid=1153075842/sr=1-10/ref=sr_1_10/102-1173777-7676109?s=books&v=glance&n=283155)🙂