There are two methods of dechlorinating and refilling tanks;
1. You add enough dechlorinator for the whole tank's volume to the tank and then refill with straight tap water. This method is good for big tanks that are impractical to do with buckets, as you can add the new water through a hose. You need to have your filters switched off and it's best used for well matured, stable tanks with robust bacterial colonies in the filter.
2. You dechlorinate each bucket of new water, before you add it to the tank. You only need enough dechorinator for the actual amount in your bucket. This method is best for small tanks, and possibly ones that are cycling/newly cycled; those tanks need a bit more TLC than older, more mature set ups.
