Investigate the cause of illnessIn order to treat fish properly you must be able to investigate the cause of the problem as well as the symptoms. If, for instance, a disease is present due to bad water conditions, then treatments will not be effective unless the water is first brought back to ideal condition. Bringing water back to ideal conditions may involve the use of chemical mediums such as activated carbon or even stronger filter mediums. These items often remove treatments from the water so they must be used first and removed immediately before a course of treatment begins. In a similar example, if a fish is ill due to bullying, or any stress-causing factor, treatments will not work until the underlying cause is removed.
Carry out minor maintenance before treatingAs mentioned above, it is vital that the environmental conditions in the aquarium are at ideal levels before treatment begins. This is in part because most treatments can only be effective if they are working in conjunction with the fish's natural defences and immune system. For the fish to provide a suitable defence to fight the disease, it must have a minimal amount of stress, which requires ideal water conditions. It is wise therefore to carry out some basic maintenance before starting a course of treatment. It is important however, to avoid excessive maintenance since this will only cause disruption to the environment and further stress the fish. A small water change (no more than 10%), quick clean of filter media in tank water (avoiding excessive cleaning), and substrate siphon is all that is required. Gravel or substrate cleaning using a gravel cleaner/siphon is very important since this will remove waste debris, which is an ideal place for harmful bacteria to live.
Do the entire courseSome treatments require a course to be carried out over several days, if this is the case it is very important that the whole course is completed, even if the fish appear to recover half way through. This is because the treatment may be designed to kill particular pathogens in different stages of its life cycle, thereby preventing re-infection of the fish.
Check the advice and instructionsIt might sound obvious, but thoroughly read the instructions provided with any treatments. Some treatments can adversely affect certain species such as loaches and invertebrates (e.g. shrimps) and may require different dosages to be used with these species. A small number of treatments can also kill the useful bacteria in the filter, in which case the water quality must be carefully monitored to avoid any adverse effects.
Setting up a hospital tankYou may hear about setting up 'hospital' tanks to treat fish, or isolating the affected fish within the main aquarium for treatment. Whilst this can be effective in some situations it is often counter-productive since the catching, transfer, and confinement of fish will cause additional stress. If the 'hospital' tank is newly set-up it will also be prone to water quality problems, which will adversely affect the fish and prevent effective use of treatments.