Every day the WWM crew receives around 30 queries from fishkeepers around the world, covering topics from every conceivable branch of the hobby. A sizeable proportion of those queries have one thing in common: too many fish in too small an aquarium.
Overstocking is sometimes appropriate, for example in situations where highly territorial cichlids are being maintained. Expert fishkeepers will understand the problems overstocking causes, and will be able to take appropriate actions to prevent poor water quality and disease. But more often than not, overstocked tanks are mismanaged, and the results are never good.

The key problem is that the smaller the tank, the easier it is to overstock it. Making things even worse is the fact small tanks are inherently unstable. Overstock a small aquarium and you’re asking for trouble: pH drops more rapidly and water quality degrades more quickly. Big tanks leave you some wiggle room, so that when things go wrong there’s usually time to correct them. When small tanks go bad, they go bad quickly, the result being lots of sick or dead fish.

Unfortunately, small tanks are very attractive to inexperienced fishkeepers. For those people shopping for their first aquarium, even a ten-gallon aquarium looks huge. Cost is an issue too, with newcomers to the hobby all too often looking for the cheapest system they can afford, rather than the system best suited to their needs.

Goldfish pose the classic conundrum: because goldfish cost only pennies to buy, the assumption is that they’re cheap pets, and that you shouldn’t need to spend much money to keep them. Here in England, you could buy a goldfish, a plastic bowl, and a packet of flake food for under ten pounds (less than $20). Quite clearly, a cheap hobby... or so it would seem.

Goldfish cannot be kept in bowls, and they cannot be kept cheaply. They’re big, sociable animals that need - at minimum - an aquarium around the 30-gallon mark to do well. Besides the tank, you’ll also need a decent filter, though a heater isn’t necessary except perhaps with the more delicate fancy varieties. So while your goldfish might cost less than a candy bar, even a basic goldfish aquarium is going to cost well over £100 ($200) to put together.  

The craze for ‘nano’ reef tanks has perhaps made things even worse. If marine aquarists can keep corals and clownfish in a 10-gallon tank, then how difficult could it be to keep some guppies in a 10-gallon tank? What casual aquarists don’t realise is that successful nano reef tanks are expensive to set up and have to be very carefully monitored and maintained. Aquarists who succeed with nano reef tanks have invariably started out with a bigger reef tank first, learning all about water chemistry, livestock selection, and water quality management. Until you’ve done the same thing on the freshwater side of the hobby, setting up a freshwater tank smaller than 20-gallons is not to recommended.

Several of the articles in this month’s Conscientious Aquarist focus on livestock suitable for small tanks. There’s an article by Lonnie Lindberg on one of the best fish for the small freshwater tank, the betta or Siamese fighting fish, Betta splendens. Like the goldfish, this is another species often thrown into a bowl without any thought about what its maintenance requirements actually are. An article on crayfish by Justin Pierce outlines the needs of these interesting and hardy crustaceans. Crayfish are enjoying a bit of a vogue at the moment, and because they don’t require much space, they make good choices for someone after a small aquarium oddball. My own piece of stocking 5, 10, and 20-gallon tanks tries to fill in a few of the gaps in the community tank literature, offering some tried-and-trusted species that work well in small aquaria.

Small aquaria can be fun, and properly set up and maintained they have a jewel-like quality that attracts the eye and piques the interest of even the most jaded observer. But they certainly can’t be recommended for beginners.

Neale Monks