I f you’re curious about keeping fish and considering buying a 20-gallon aquarium, you’ve come to the right place. It’s hard to know where to start when choosing fish, and tank size is just ...

It won’t shock anybody that a koi fish needs a much bigger space than a goldfish or guppy. A 20-gallon tank is suitable for a single goldfish. Yet, these fish can quickly outgrow their aquariums ...