WATER CHANGES: Providing your tank is not overcrowded, once a week is fine, just remember though the more fish the more water changes. Make sure you use Dacron or the like to clean the inside of the glass, if gravel is used clean it well with a gravel cleaner obtained from aquarium shops. Remember parasites breed in the gravel at various stages in their development, bare bottom tanks make the chore much easier. All fish including discus pick up harmful bacteria while foraging for food in the gravel, any left over rotting food can be a source of harmful infection. A fish under stress, particularly if bullied, overcrowded or in poor water conditions usually fall victim to bacterial infections such as columnaris; a bacteria that favours high water temperatures. Death can be swift and secondary infections can be plentiful. By keeping water conditions right and the tank free of uneaten food and faeces such problems can be averted.