RO/DI is the best way, yes, but not the only way and they are very expensive! I use something called PRIME which is a liquified agent which takes out all the silicates ammonia, nitrate, nitrite, etc... out of the water. This stuff is cheap, and works great, and 1 drop cures 2 liters. Get some of this and if it dosn't work then something else is probebly needed. GOOD LUCK