ich salt dosing question

Yes, a SW dip will do the same thing but doesn't treat the ich in the tank. Your loaches are very sensitive to salt. Whever treating FW fish w/salt, add 1tbsp/10g, raise the temp to 86 & do huge (80%) WC every other day, being sure to clean the substrate, for a week.
See: TREATING FW ICH
Now, if you only see a few spots, you may not find it necessary to treat so aggressively but if you have loaches, they can succumb to the parasite & die very quickly.
 
You would follow the directions on the marine salt bag for mixing. Probably a SG of around 1.018 would do though. Dip for as long as the fish can stand--up to 1/2 hour, for extreme cases. Keep a close eye for stress.
 
Opinions vary as do treatments. I used 2 tsp/gallon and my cories, rummys and snail handled it fine.
 
Well, I've left it at 1 1/2 tsp, as I didn't want to bump it up higher if I didn't need to. Fish are all doing well. I'm doing a massive water change today, and replacing the salt as well as the water. There's been no spots since I added the salt (there was only ever 2 spots on the one fish). I figure I'll leave it salted for another 5 days or so, then do a big water change and not replace the salt.
 
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