I am doing a 25% water change which will be about 4000 gallons.
I have always added dechlor after I have totally refilled the pond.
Someone told me I should add the dechlor to the pond before I add the new water.
If I add the dechlor first and it takes several hours to refill the pond will the dechlor stay active that long?
Which is the best way?
Thanks in advance!