I have a 20 gallon aquarium with a few pieces of live rock. I had 2 clownfish in it. Im in college and when i returend one of them had died. My dad said the one that died had white spots over it. so i am assuming that the fish died of ich. I know one way to clear the tank of ich is to lower the salinity. I was wondering how low I can take the salinity with my green brittle star in it. Any ideas would be great.