Lots of us can remember having childhood goldfish that were won from the fair, or bought by our parents who carefully swapped dead fish with identical replacements in the hope that we'd never notice. As a result, many people still regard a bowl as a suitable environment for a goldfish. Although the term Goldfish bowl seems as natural as Rabbit hutch, dog bed or cat flap, it belongs with terms like bull fight and mouse trap as labels which relate to animals in the wrong place at the wrong time. Goldfish will survive quite appalling conditions for longer than many fish, with the result that an animal which can live for more than twenty years in good conditions will endure a few years of poor water quality before finally succumbing. Now that we have the lecture out the way, lets look at the reasons why they're unsuitable.
Goldfish are potentially large (up to 30cm/12") messy pond fish that generate a lot of waste, both visible and invisible. Although most bowls are too small for their unlucky inhabitants, it is the lack of filtration that is the biggest issue rather than the size and shape. New generation fish bowls such as the Biorb provide the classic bowl shape with the essential ingredient of efficient filtration, which removes the toxic fish waste which otherwise poisons the fish, who is after all, unable to pop out to use the loo! Neglected fish bowls also develop these filter bacteria but have to start from scratch when the whole thing is cleaned out. The lack of space causes an otherwise healthy fish to become stunted and develop problems with internal organs which can remain unseen but deadly over time. To give your goldfish a happy and long retirement, move him into a nice garden pond or large aquarium where he can grow old gracefully.
There are a few species of fish that are perfect for small, unheated tanks or bowls with filters. Ask your local branch about the fantastic and versatile White Cloud Mountain Minnow.