Ditto, I never mix with water. I add a portion of each premeasured amount of Safe as I am filling.The current directions for Safe treat 1.25ppm chlorine/1ppm chloramine. Check your water report for how much chloramine or chlorine you have, and dose your tank based on the total tank volume, regardless of amount of water changed.
If your water is treated with 4ppm chloramine or 5ppm chlorine, use 1 teaspoon per 200 gallons (instructions before 2014).
I use these spoons for my smaller tanks https://www.amazon.com/Norpro-Stain...ash+measuring&qid=1565274621&s=gateway&sr=8-3. I use the drop spoon (about 1/64 of a teaspoon) for every 5 gallons because I know that I have 4ppm chloramine.
I don't bother mixing the safe in water before putting it into the tank. I put it in the same area as where I am going to refill. I have had fish try to eat the undissolved particles because they think I am putting in food, and have noticed no immediate side effects from doing so.
I'm not personally thrilled with the post 2014 change in directions, I suspect that a lot of people are under-dosing.
I discussed that change in detail in this past topic:
The Dumbing Down of Seachem
Approx 3 yrs ago Seachem decided that due to customers not being able to add 1+1 and divide by 2, they would simplify their dosage instructions on Seachem Safe. This topic was brought up by @pops , to which I added my 2 cents...
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