What is the transition care from freshwater to brackish water fish?

It's not often that you will need to move a fish from freshwater into brackish water but it does happen, ie when bumblebee gobies or mollies have been kept in fresh water. The best thing to do is to put the fish in a quarantine tank and gradually increase the salt level until it matches the level in the destination tank. Fish should be provided with hiding places during this time and if it is not possible to run a cycled filter on the tank, treat with ammo-lock or similar. Do not do water changes if you can avoid it, because fluctuations in salinity at this time are not a good thing

• use ammo-lock (or nitrate resin if you have a cycled filter). Add

salt slowly - about 1/2 teaspoon/gallon/day. Dissolve the salt fully in water and add it over a few minutes. When the salinity of the tank matches the salinity of the tank you intend to put the fish in, you can move it across presuming the quarantine period has been long enough. Remember it is not possible to do this with all species. Species that can be successfully adapted to brackish water include all common livebearers, many cichlids and most gobies and gudgeons.