Like the saying goes, 'a good start is half the battle's won'. This couldn't be more true in aquaria.

Cycling a new fish tank
Before you even aquire your fish, you should make sure that your fish tank is cycled first.

Introducing new fishes
You don't want to be suddenly chucked into your neighbour's house to stay for life. Why would you do it to your fish?

Many people like to add all kinds of chemicals to the water. However, many of them just benefit the seller, not the fish.
The reason why chemical addictives are useless is that they often 'treat the symptons not the source'. As a result, the problem is not solved, just the disaster is postponed. If use chemicals to keep the balance, then you will have to keep using them. I suppose this will make the seller very happy indeed. Just remember that man-made addictives are not present in the water in nature, but the fish are healthy and happy.
If you are just interested in postponing the problem, then changing the water will be a much more effective 'solution'.

In this section, you will learn you can add to the water. Naturally.

If you need to analyse your aquarium water parameters, you can either bring a small sample of the water to a local fish shop or you can use commercially available test kits to test it yourself.
Water parameters and what they mean.

Here you can tell from the symptoms what your fish is lacking.
Proper nutrition is better than any medication because it is treating the source.

As all living things live and die, sickness and diseases are part and parcel of life. In this section I will teach you how to recognise the most common fish diseases, as well as how to fight it. In most cases, your fish will get stronger and will gain increased immunity against future attacks.

This section will deal with breeding fish. If your fish has a short lifespan, you cannot make it live longer. However, you can extend its bloodline by breeding them raising the fry. This way, you can keep the family going for generations. However, note that this practise is not advisable for too sentimental people, because you may one day terminate the bloodline due to unforeseen circumstances or accidents. Expecially if you have bred the 'family' of fish for generations, a break may cause a tremendous feeling of lost.