"2. Measure the length and width of your tank and multiply them. Then, divide by 13. This is the maximum number of inches in fish you can keep at adult size. (Reasons: Why not gallons? Well first, comparing linear lengths of fish to volume of tank is comparing apples and oranges. But, it goes deeper than that. While the volume of water in a given tank is important in diluting the nutrients/waste, surface are is likely more important for gas exchange. Also, fish do not swim vertically, they orient themselves to gravity and swim horizontally, another reason why Surface Area is far more important than Volume.)"

I got this stocking guide from a pretty reliable website...

So I did the calculations. My ten gallon tank is 12x24. My answer was just a little over 22" of fish could go in here. Is that really true? Did I calculate wrong???

I know this is just a very rough guideline by the way, and that a lot of fish can't live by rules like this. I am planning on getting another ten gallonish tank and want to put a school of black neon/cardinal tetras in there, along with maybe a female betta, pair of sparkling pygmy gourami, OR a pair of african dwarf frogs. How many fish can I fit in here? Other suggestions of compatible fish are welcome

id go for 15-18 inches of fish max, and stock it up very slowly with regular water changes

Thanks Kev I will! When I get the tank, I will do a fishless cycle And hopefully I'll be able to afford a ten gallon. I might have to settle for a five.