Most fish keepers often recommend large volumes of water for most fish, it may seem especially large for beginners, as most keep fish in smaller volumes (compared to 10, 20 & 30+ gallons). And to some, it may be quite shocking. Why do they recommend so much? Although it might seem unreasonable, some fish tend to be healthier in larger volumes. Here are some benefits for having a larger aquarium.
Fish have more room
Larger aquariums are less likely to get as dirty as fast as smaller aquariums would
It’s Easier to find heaters & filters that are big enough to fit the volume of water
More area for decorating your aquarium
Goldfish & Bettas are two of the most commonly kept fish in 1 gallon bowls. Most fish keepers recommend 5+ gallons for Bettas & 55+ gallons for Goldfish (Fancy Tail Goldfish being one of the smallest Goldfish 55 gallons of water, while the common Goldfish 100). Although some say 2.5 gallons of water is also an exception for Bettas.
Of course, fish can actually live in small aquariums, just according to most fish keepers, they tend to be healthier in larger volumes. Also try to clean the tank at least once a month & feed them regularly if your looking for healthy fish.