You can treat Ich without the heat, but it takes much longer. Heat just speeds up the cycle. The Ich parasite is a protozoan that is too small to be seen at first and may be in the fish's gills, their mouth, nose, under the skin, etc.
At the stage that you see them as salt specks they have erupted from the skin. After a time on the skin as specks, they fall off and to the substrate where they form cysts that, after multiplying inside, rupture and release the free swimming protozoan that, again, is too small to be seen, but it is at this stage that it is vulnerable to the salt and the Ich meds.
The heat speeds up the cycle so that at 84-86 degrees the specks fall off in about four days, and then after a couple of days the cysts rupture and the free swimmers die in the saltwater.
You can treat Ich with salt alone, but unheated it could take up to six weeks to complete the cycle. You might want to go ahead and invest in a good heater.
What size tank is it? A 50 watt Marineland Stealth VisiTherm heater would be fairly inexpensive and could adquately heat a 10 gallon, or less, up to probably 86 degrees.
I think I would want to speed it up as much as possible to reduce stress to the fish.
It is 2 Tsp per gallon. Some say a tablespoon, which is 3 tsp per gallon.
I'm treating for Ich that came from some plants I got at my lfs, and I've been doing 86 degrees for 4 days, 2 tsp of salt per gallon. I've done approx 80% waterchanges each day, (because I had lost my biofilter due to a power failure and so essentially I have an uncycled tank), and put back into the tank the proper amount of water with 2 tsp per gallon.
Today all the specks are off, I expect that by day six the free swimmers will all be dead, but I will go for another week just to be dang sure.
