I have been using this water conditioner for years for water changes but also when I introduce new fish. It is very efficient. I buy the big bottles and keep a small one which makes it easier to dose and avoid over conditionning the water. I really recommend Aquasafe and I have tried many products over the years. Dosing: 1 small squirt per two litres... yeah I know, this is very approximative but frankly it's fine, my fish have never complained (or died by the way!!) I have rasboras, cardinals, tetras, angel fish, corydoras, ottos etc!