White spot is a protozoan parasite that infects the gills and skin of fish.  It is almost always present in the aquarium, but presents no problems if the fish are happy and healthy.  Once fish have been infected with white spot, they often get a resistance to it, so rarely become infected badly again for at least the next 6 months if conditions remain good.  White spot is encouraged by poor water quality and stress, so maintaining good water quality and minimising stress to the fish will prevent any fish losses.  The white spot itself does not kill fish, it is the secondary bacterial infections that cause problems.

All it takes is some sort of stress to bring this parasite out. This could be anything from temperature fluctuations, poor water quality or even introducing new fish.

First Raise your temperature if you can, up to about 28-31 degrees, this will vary with different thermometers.

Option 1:

Treat the aquarium with Tri-Sulpha as this will also aid in healing any secondary bacterial infections. One downfall with this is that it can knock back your bacteria with prolonged use.  Re-dose every 3 days (after a 25% water change before any re-treatments). You can also add salt at the rate of approx 5gm per 10litres whilst dosing with Tri-Sulpha.

Option 2:

Using Products such as Rapid White spot remedy or other malachite green/acriflavine based products. These must be used at half the dose rate recommended if you have fish like loaches. Follow the instructions on the package for dose rates. These products work well in a controlled environment (low in organics) but can stain your water and ornaments, this will over time break down with light, and it can also take longer for your bacteria to re-establish as a result of the staining of your filter media, so read the instructions carefully. You can add Salt whilst using this product also.

White spot will always get worse before it gets better.  Just keep up the treatment and monitor your water quality.  Stick to minimal feeding of the fish if you can during this time. You can only kill white spot when it detaches it self from the fish (free swimming) so keep medicating until it is gone.

Also if you have any activated carbon/charcoal in your filter then take these out prior to medicating.  Turn off any light or U.V Sterilizers whilst medicating as these will break down the medication.

Keep in mind that most medications, particularly those that are salt and malachite green based, will also affect your plants, so a bare quarantine tank with a basic sponge filter is the best to treat in.  If you have a planted tank and do not wish to use medications, the high temperature alone will help control the white spot, assuming the planted tank water quality is 100%.  You can remove touchy plants that you wish to save, and place them in water without fish, and after 48hours these plants will not have any white spot parasites left on them and can be placed in another tank or held until treatment is complete in the original tank.

For long-term prevention, a U.V Sterilizer may be added to the aquarium, as water passes through the unit it will kill any free-floating parasites or algae particles. This is not a cure but only a preventative measure and 99% of the time stops or slows down the outbreak before it becomes an issue.

A quarantine tank is also recommended for all hobbyists. Always put new fish in a quarantine tank for at least a week to monitor their health and catch any parasitic outbreaks early.