My first post... I have a Rio 180 that's been in service about 6-8 weeks. I use the internal filter and an Eheim 2213. I have the normal 2 T8s of unknown age (second hand tank) and 1 new T8 (so 90W in total). Currently, I change about 10% a week with water that I have taken directly from the mains (i.e. unsoftened) but heated to the right temperature with a spare tank heater first. I'd like to use EI method, but on my Rio180 that means swapping 90 litres a week. I presume when most people do this, they use a python arrangement and get the water to right temperature by mixing hot and cold water. I have a Kinetic water softener (the one that runs on water pressure rather than electricity)... so that means I would be adding artificially softened water if I added hot water. I presume if I just added cold water, my fish would freeze! Am I OK to use the softened water?