Well,you can't just put fish in a tank with that low of salinity after being in a tank with normal salinity.There is a process to it.First,it has to be a fish only tank,only fish.Then over a weeks time,you lower it down to 1.09,no lower,no higher.It has to be exactly 1.09.This will cause the ick to burst and die.Ick will even make it with the salinity at 1.10.You keep it at that for 3 weeks then slowly bring it back up.If your treating a fish only tank,you could also use copper.Also,a U.V. steralizer is recommended.I say recommended because I don't have one but they do good from others experience.HTH