[quote=RichToyBox]Hard water is really not a problem. [quote]

Sorry. When I typed in my post I didn't realise this forum doesn't support "more than" arrows. It should have read that the GH is more than 16, i.e. off the scale on the test strip and classed as very hard water. I was a bit concerned because, from what I've read, for most fish, including GF and Koi, moderate to fairly hard water is preferable. When you say the KH is at the low end, what should it ideally be? I live on an island, so seashells to put in the filter are not a problem for me if you think it is required to raise the KH.

Bill.