Full Size of Guppy Fish?


Topic: Just like the title states, I need to know how large guppy fish grow to? I have a 20 gallon aquarium and am wanting to add more guppies. But if they grow fairly large.. then I can’t have that many inside one tank. Do they stay pretty small? What is their full growth size? Need some help from guppy keepers.

*Awarded Answer
Posted by Kristy M:
I happen to love guppies too! Awesome that your asking this great question before just jumping into actions too fast. To answer your question, female guppies grow to 2 inches and the males are a bit smaller at around 1.5 inches. Guppies are very small fish but pack a tremendous appearance.

As far as properly stocking your 20 gallon tank, figure on 1 inch of fish per every gallon. Guppies are a bit different though. You can have them in closer parameters then other fish and do quite fine. I have a tank that is a bit over populated with around 20 guppies within 20 gallons of water. The reason is because they sex and multiply so fast and that’s just what I have room for. Remember, if your tank is crowded you need to be more strict on keeping the water clean since the load is heavier with more fish.

Posted by Brandon K:
Overloading your aquarium with guppies is not an okay thing to do so I’m not sure why you would state that. Sticking to the general rule of thumb which is one inch of fish per every single gallon of water is the best route. It is a lot more safe to populate your aquarium based on what the future adult growth size would be and not what it actually is right now. It really comes down to what food you are using for your fish too.


Replied by Kristy M:
What I simply meant was that a lot of aquariums out there including guppies are on average overpopulated because of how fast they multiply. Not saying that it’s okay to overpopulate your fish aquarium but if you’re going to do it a little bit you need to make sure that you keep up with water quality because chances are that you might end up over populating your tanks because of how fast they breed. Sometimes I think people lie to themselves and say their tank is not overpopulated but in fact it really is.

These little fish only grow 1 to 2 inches and their bio load is very minimal so over populating them isn’t going to be as bad as other species of fish could be. I love these species of life bears tend to be overpopulated and there’s really no way of running from the idea so I that was all I was stating.

But to answer the initial question of how big or how large in size Guppy fish grow to is 1 to 2 inches. The males are a little bit smaller than the females and they only get to about 1 1/2 inches long while the females are A bit larger and grow to around 2 inches.


Posted by Danny E:
I must admit that my tanks are a little bit overcrowded too but I keep up with water changes on more of a scale then other people. I like to do a 20% water change on a daily basis and Christie is absolutely correct with a lot of tanks being overpopulated. I guess the moral the story is to try to educate beginners and newcomers to not overpopulate or text. At the end of the day you were both right on the argument so there’s no need to continue.

  • Some of the pregnant females are going to weigh more but not be any longer (Don’t forget to put them in a breeder box by the way).