With buckets you add the dechlorinator to each bucketful at the dose rate for the volume of the bucket. You use the amount to treat the new water only. My dechlorinator dose rate is 1 drop per US gallon. My bucket holds 2 gallons so I add 2 drops to every bucketful. (I can't lift anything heavier than 2 gallons
) Since I can't lift the bucket high enough to pour it in the tank - and it would cause a crater in the sand - I use a jug to scoop it from the bucket to the tank. This does the same as SlapHppy holding the fill tube above the water.
When filling with a hose, the dechlorinator has to be added to the tank, and a lot of dechlorinators say to add the amount to treat the entire tank volume, not the the amount of new water (read the instructions carefully and if in doubt email the manufacturer).