It it pretty well documented that during the first 12hrs or so freshly mixed SW
has very low oxygen content and other chemical reactions ongoing that are bad for fish - don't know if this would kill but I guess it could. I do not know why salt companies don't print this on the instructions. Most of the SW
community recommends 24hrs for the sw
to mix and aerate (with powerhead or air pump) - to get oxygenated and chemically stable. Also don't forget a heater so your new batch is close to tank temp.
Hmm, you might want to see if RO
water is available at a local grocery or lfs
. If not, I have had good luck in the past with Prime, but you might want to get another bottle of that (or other) in case it is a "bad batch". Good luck and keep at it...it will get better