Aquarium Estimator Tools

"How Many Fish?" Aquarium Stock Level Calculator

Estimate how many fish an aquarium can support

About How Many

I started How Many after the lessons I learned setting up my first 29 gallon tank. I was looking for information on how many fish my aquarium could hold. The one-inch-per-gallon rule is widely panned by serious fish keepers. Of course, exact fish capacity depends on many factors, which serious keepers carefully consider. But I needed to start somewhere. People dedicated to their hobby sometimes have trouble being helpful because their concern to do everything just right makes the hobby seem too complicated to the new person. In my research, I found the surface area rule of thumb. It is simple, but it yields a reasonable, fairly conservative result which made scientific sense to me and seemed unlikely to lead to overstocking. To give it more prominence for the benefit of new keepers, I created this website.

I have since added pages on other topics that may confuse a new fishkeeper

  • Hexagonal tanks, which are have more complex calculations for volume.
  • Aquarium substrate weight, because gravel and sand are packaged by weight, not volume.
  • Cycling, the most important thing a new fish keeper must understand before getting that first fish.

Thanks for visiting. I hope you find it useful. Contact me at the link in the footer with any questions or comments.

If you like simple explanations of confusing things, check our other websites:

Additional Credits

"Crystal Clear app babelfish" by Everaldo Coelho and YellowIcon - All Crystal icons were posted by the author as LGPL on kde-look. Licensed under LGPL via Wikimedia Commons -