Some people also use baking soda, epsom salts, and aquarium salt. You must experiment very carefully with your water, however, and make certain you know how much of each will raise your conditions by how much. They're also better pre-dissolved in tank water in a bucket before adding.
Also, always remember not to change things too quickly!
Most importantly, however, fish value stability over perfect water conditions. Rapid changes in water condition will do more harm than water that's a bit soft. You might just see how they do in your current water. That is likely to work out far better in the long run.