Mike Patterson wrote:

Needed to top up the pond, my area uses Chloramine, so I have to use
dechlorinator.

The bottle said to add 1 capful for every 20 gallons of water, but how
many gallons did I need to add, and how to calculate it, and how do I
add the stuff?

Dump it into the pond before adding the water? Could that be bad for
the fish?

Add the water then dump in the stuff? Would the exposure to chloramine
before it was neutralized hurt the fish?

Was I wasting time and emotional energy worrying about it? Well, maybe
a little bit...

At any rate, I settled on this method:

I put a clean 5-gallon bucket (God, I love those things!) in a place
where when overfilled it would overflow into the pond. Used a spring
clamp to attach the garden hose near the bottom of the bucket.
-Inside- of the bucket.

Now to calculate what's needed -

My pond has 104 square feet of surface area, so divide that by 12 to
get the cubic feet of water necessary to raise the level by one inch
gives me 8.666 (all those sixes got a bit scary here...) cubic feet.

Multiply the cubic feet by 7.48 gallons in a cubic foot giving me 64.8
gallons to raise my pond's level by one inch.

I wanted to raise the water by 2 inches, so I rounded up to 130
gallons and added 6 caps full of chemical to the 5-gallon bucket (You
remember the bucket, don't you? We left it right next to the pond.)

Turned on the garden hose and I'm thinking that this way, the
chloramine-laden water will have to go through the
de-chlorinator-laden bucket to get to the pond.

If anyone thinks I'm off track here, please let me know.

Won't hurt anything, but it's fancier than needed. I know plenty of freshwater
aquarist who just dump the water conditioner in the tank, then top it off (if
you're using a Python to vac then top off the tank, this is by far the
least-hassle method).