How many gallons per fish in a freshwater tank?

There is no definitive rule, but the general consensus is that you need about 1 gallon of water per inch of adult fish. For example, a 2 inch goldfish would need at least 2 gallons of water.

Keep in mind that certain species may need more or less water than average, so it's always best to research the specific types of fish you're keeping to ensure they have enough room to thrive.

Other factors to consider include:

- The size and shape of the tank: A long, narrow tank will provide more swimming space than a short, wide one.

- The number and size of plants and decorations: These can take up space that could otherwise be used by fish.

- The filtration system: A good filter will help keep the water clean and reduce the amount of waste that builds up.

It's always better to err on the side of caution and provide your fish with more space than you think they need. Overcrowding can lead to stress, disease, and even death.