Fish per tank

Question
I've heard that the rule of thumb for the number of fish in a tank is one inch of fish per gallon. However, this always confused me because I'm pretty sure you shouldn't keep a five inch fish in a five gallon tank. However, many people have 10 or 20 gallon tanks with large schools of tetras or other small fish in them with no problems. And does this rule also include non fish such as snails and shrimp? Example: In a five gallon tank is one fish, three shrimp and a snail is the limit?

Answer
Hi Benjamin

It's a general rule of thumb that it's one inch of adult fish per gallon of water. That rule is assuming you will put a certain size fish in an appropriate sized tank, and of course, a 5 gallon tank is not appropriate for a 5 inch fish. But a 5 gallon tank could hold 5 one inch fish. When it comes to larger fish, I usually multiply it times 5. So a 5 inch fish could go into a 25 gallon tank. A 12 inch fish would need a 60 gallon tank etc. This is not saying that you can only put the 5 inch fish in a 25 gallon tank or the 12 inch fish in a 60 gallon with no tankmates. You go back to the rule and figure 5 of the 5 inch fish will fit in a 25 gallon. However, 5 of the 12 inch fish would not fit in a 60 gallon tank. The larger the fish, the larger the ratio.

I can't answer your question about snails and shrimp because I don't keep nor do I recommend keeping crustaceans with tropical fish, it causes too many problems.

Now, having explained the rule to you, in my opinion, the general rule applies to people who are just starting out with their tanks to keep them from overcrowding their tank before it is cycled and ready for that load. There are many expert fishkeepers, myself included, who have been keeping fish for years and will overcrowd their tanks. I've been keeping fish for many years and I pretty much know what I can get away with and what I shouldn't try. I also keep multiple filters on my tanks that are equal or greater to twice what the tank needs. For example, I keep a 20 gallon filter on a 10 gallon tank and so on.

I really hope this information is insightful to you and helps you. Thanks for using AllExperts!

Richard