The employee was correct, but he was also not aware what happens with the ammonia byproduct with Stress Coat.I had also thought the same before, but after some research, I realise Prime is a better choice. I've used Stress Coat for majority of my years in the hobby and just started using Prime.
StressCoat bonds/nuetralizes with the chlorine and chloramine. Unfortunately, one of the byproducts is ammonia (Chlorine + Ammonia = Chloramine).
Prime does the same, but also bonds/neutralizes ammonia.
Both are supposed to help promote the slime coat in fish.
With Prime, a small dosage can handle allot of water.
What most people do is add the dechlorinator in the tank before adding the water. I do this on my 125 gallon tank. On my 20 gallon longs (Zebra and RCS tank), I use aged water, which has already been dechlored and treated. Since they are smaller tanks, small water changes can effect the inhabitants in the tank. So I make sure the water is already treated and heated.