If you’re just getting started with your first aquarium, you may be wondering how many fish you can keep in a single tank. While the answer depends on the breed of fish and their size, guppies produce a fairly small amount of waste so you can get away with having a larger school of guppies in a smaller tank than you could with some breeds. Here’s a basic guide to the number of guppies you can have in one tank.
General Rule of Thumb: One Guppy Per Gallon
As a general rule of thumb, stick with one fish or guppy for every gallon of water in the tank. If you’re an experienced fish keeper, you can get away with 15-20 guppies in a 10-gallon tank, although it’s best to start off with less fish in the beginning. Make sure you can keep two or three guppies alive for at least four months before you add more. Overpopulating the tank is one of the most common beginner’s mistakes that leads to dead fish!
Keep in mind that guppies are live birthers and they will multiply very, very quickly. You may have your first batch of fry within just one month and your female guppies can get pregnant again immediately after giving birth. If you want to grow the size of your tank, you can save your fry and transfer them to a separate breeding tank until they grow large enough to avoid being eaten by grown guppies.
If the tank has only guppy fry, a 10-gallon tank is definitely large enough to safely handle 100 fry or more. Just be careful that your fry don’t get sucked into the intake tube on your tank’s filtration system!
If your tank begins to get overpopulated with guppies, there are several things you can do. You can read more about what to do with extra fry.