Previous Questions

Why do I have to remove the carbon filter when using treatments or medicines?

The carbon in the filter removes contaminants and chemicals from the water.
Therefore, if it is left it in whilst treating the tank for something, it will remove the treatment and whatever you were trying to treat will continue to be a problem.

Once the course of treatment has been completed, carry out a 10% water change and replace your carbon filter.

The only treatments in the King British range where removing the carbon filter isn't necessary are King British Filter Aid+ and King British De-Chlorinator.