The one-inch-per-gallon rule is a general rule of thumb used to determine how many gallons of water a fish will need in a tank. While this rule can certainly be helpful in some situations, such as setting up a holding tank for cleaning or an emergency tank, it should by no means be used to make a tank that you intend to keep a fish in for the rest of its life. So, here’s why the one-inch-per-gallon rule simply doesn’t work.
It Doesn’t Take Into Account Waste Output
The most glaring issue with the one-inch-per-gallon rule is the overproduction of waste. While you may think having 10 neon tetras in a ten-gallon tank is just fine, the amount of waste buildup will skyrocket quickly. This means that all the other tank levels that you need to keep in mind, such as oxygen, pH, and nitrates, will go completely out of whack. You’ll end up having to check and clean your tank much more often.
Fish of Different Shapes Don’t Fit the Same Way
All fish are different, and one rule will not apply to another. For example, five two-inch common Goldfish will not fit the tank the same way a bala shark or African leaf fish does. You must keep the length, size, and shape of a fish in mind. Your fish have particular swimming space needs. If they don’t have enough room to hide, turn around, and explore, they can quickly become stressed and sick, which can be fatal.
You’ll Have More Than Just Fish in Your Tank
Lastly, you’re going to have more than just fish in your tank. The one-inch rule doesn’t consider the fact that you’ll have substrate, decor, filtration systems, plants, and more. If you get a 10-gallon tank for 10 neon tetras and then put all your equipment and accessories in, that’s a recipe for an overcrowded tank.
Your best bet is to use a water displacement method to see how much space your decor and equipment will take up and how much space is left over. If the amount of space left over in your tank isn’t at least double the one-inch-per-gallon rule, then you need a bigger tank.
While the once-inch per gallon rule doesn’t always work, it’s a good starting point if you want to stock a tank or quickly set up a holding tank. If you’re unsure, talk to your local fish keeper, and they can give you a good idea of how much space your particular fish need.
