it was virtually impossible to overdose
I never said that - but I have read that a number of times over the years about sodium thiosulfate. Personally I have never used sodium thiosulfate - we have had chloramine treated tap water here for many years. I started with Prime, then went to Cloram-X, then approx. 10 yrs ago when I found a company that would ship Safe to Canada, I began using Safe and have never looked back.
Either way, I would highly recommend not stopping here, and finding out EXACTLY what your local water supply company is using for disinfectant, and at what level. (mg/l or ppm). Without that data you are playing by guess or by golly, as you will have no idea how much conditioner you should be adding at each water change. The info on the water conditioner label only helps those who know what level of residuals they are treating.
As an example, in my case I have approx. 2ppm chloramine year round, a bit more during heavy rain, and during spring run off, so at those times I add slightly more than normal. But I know from the very get go that I am treating a baseline of 2 ppm. not 1 ppm, not 1.5 ppm, and not 4 ppm. It makes a difference, to your wallet, and potentially to the fish as products such as Prime & Safe are reducing agents, and when they are done reducing chlorine, they will look for something else to reduce, such as oxygen. You CAN indeed overdose with those products - I have seen it first hand. Not a pretty sight when hundreds of $$$$ worth of fish get dead from something as basic as operator error.
