Do you have a heater in the tank now? If not, you really should - especially with your frigid Canadian winters. Temperature fluctuations stress fish and leave them vulnerable to diseases. Most fish do well at 78 - 82oF
5 watts per gallon is the norm, so 50W should be OK for your 10 gal
. Perhaps 75W if the room gets chilly at night.
To treat ich, raise the temp over the course of a few hours to 88oF and leave it there for three weeks, no less. Ich be gone - almost guaranteed.