HappyGeorge
Fish Herder
Personally I like to wash with tap water first because I want the pressure from the hose driving the water through the sand, I do then wash in RO. I'm not sure about the risks from tap water not an expert but coral sand doesn't hold much water. I had 40kg which had sat over a bucket to drain and it was only about half a litre so any trace elements would probably be tiny but I would probably want to know what the breakdown of the tap water was. I have to say when my corals were in the bath waiting to go in the tank I had to top it up with about 10 litres of tap water due to poor timing and planning but was absolutely necessary, despite this I have never tested any Phos or Nitrate despite my tap water having 20ppm Nitrate.
I'm not saying it is a wise thing to do but I can only comment on my experiences.
I'm not saying it is a wise thing to do but I can only comment on my experiences.