Goldfish are usually purchased from the pet shop at a very small size. They can grow to around 30 centimetres, depending on the type of goldfish.

The fancier ones, such as pearl-scaled goldfish or the red-caps grow less rapidly and to a lesser size (but are extremely cute fish !!). Although they don't grow as big they are more sensitive to water quality, so my suggestions below still apply.

My somewhat basic guide suggests ideal conditions. Goldfish can be kept otherwise, but the efforts required to keep them healthy would be definitely a chore, and if you are at that level of fishy enthusiasm, then you won't need this site.

* Firstly, you want to work with a minimum of around 50 litres per goldfish.

This would mean that in a 100 cm tank, you would have just 2 goldfish, and yes, when they are small this would seem ridiculous. Remember that given that space they will grow to full size. Due to the stability of that amount of water they will remain healthy, and also you will only have to change one quarter of the total water every 2 weeks, assuming daily, controlled feeding.

You could use a smaller tank, such as the 45 and 60-litre tanks available, The snag with these is that the smaller tanks restrict you to buying 2 small fish and exchanging them, say every 8 - 10 months, and not every pet shop owner will do this. Or resorting to large weekly water changes in an effort to keep the water quality optimal.

A small tank will also prevent the goldfish from growing fully - you will end up with a stunted fish, so you will never see your fish at it's full potential.

* Secondly, you need to get a long, horizontal tank, as opposed to a narrow tall goldfish tank.

This is because goldfish need lots of oxygen in their water, and the bulk of the oxygen exchange happens at the water surface, so the bigger the water surface the better.

* Thirdly, aim to get dark gravel for your tank - this serves 2 purposes:

It makes the fish feel more secure as they expect the ground to be darker than the sky, which has the benefit of dropping the fishy stress levels, which results in a happier, healthier fish - Which also means less stress for you (medicines are expensive, after all...)

Also, fish tend to want to blend in somewhat with the ground - to avoid predators, in the wild - so making the gravel dark will stop their colours from looking washed out.