Yes. I dissolve it in hot water. It won't all dissolve at once. Check these posts in Spidergrrl's thread by Coryman:
A couple of points here I feel need to be said. Firstly let me dispel the myth about Corys and salt. It is total Bunkum, Rubbish, or any other work that is safe to say here, that means whoever started the old wife's tail about Corys and salt, is talking garbage. The only Catfishes that do not like it, or have a reaction to it, are the "Naked" ones and not all of these react badly to salt. Salt is a very good treatment to irradiate many parasites, but it needs to be at the right strength (4oz per imperial gallon), it is the same in reverse with marine fish, treating them in soft fresh water. It starts to get complicated from here on so I will not delve any further, there are marine biology experts out there that can explain far better than me. There are three so-called pygmy Corys, C. habrosus, C. hastatus and C. pygmaeus, all three will tolerate the salt dosage I have mentioned, albeit not for a great length of time, may be a minute or so. However adding a little half a teaspoon per imperial gallon, to the tank water will do them no harm what so ever. To give you an actual example, I treated a 10 gallon (IMP) tank with 2 lbs of rock salt to irradiate an infestation of leaches. I had caught and moved all the fish, or so I though, but to make sure there would be no more leaches I left all the furnishings in the tank and it was some ten minutes after the salt went in and dissolved, that I discovered three C. pygmeaus were still in there. They were duly removed and suffered no ill effects at all, one was a large female and she went on to produce many fry and lived to the grand old age of 12 years. The fact that you have snails, friendly ones I take it, I would not add any salt.
This is the link
here
I am going to guess that if you need more than that 1/2 tsp per UK gal (I don't think I would get too excited about the difference between a usg and an imperial--I add salt to my tanks like I add salt to my food, sparingly and by a cooks measure) then you would need to remove the Cories and dose the tank heavily like Coryman mentioned he did for leaches.
Just to say I have added a small amount of salt to the sorority tank for my girl that suffers from some kind of face thing--maybe a fungus. There are 3 Botia straita and 3 ADFs in that tank. They don't seem to be a bit bothered, and I feel safer for my girls.
Another thing to remember is only replace the amount of salt that is removed from the tank in water changes. Do not redose a full amount.
