Freshwater tanks and fish must work as a team: they must match. In other words, if you plan to have a lot of fish, you will need a large tank. If you have large fish, you will need a large tank. If you plan to have aggressive fish, you may choose to have a small tank to keep one single, aggressive fish in. The type and number of fish you have and their specific needs will change the type of tank you get.

Here are some tips to help you on your quest for the right freshwater tanks and fish:

• Tank size – a rule of thumb that will help you match the right size tank with the fish you want is this: for every gallon of water, you can have one inch of a slim-bodied fish. This is not a strong and true rule, though – consider the type of fish you have. Consider how big it will be when it matures. And for medium-bodied fish, for every gallon you can have about ½ inch fish.
• Fish number – how do you know if you have too many fish for the tank size you have chosen? A few signs of having too many fish are, potentially: water dirties quickly, tank smells, listless fish, stressed fish, etc. Be sure to monitor your freshwater tanks and fish to ensure that all is well.