Thank you for the comments George.
Ill give you full credit for the white brackets, I didn't even know they existed, so cheers for that.
The plan with the HC, is to keep an open sanded area at the front, so trim the HC regularly. I haven't worked with an aquarium with a depth like this before, so i find it great to give a nice open space at the front.
At the moment, we are changing about 30% of the water a day. I'm using 100% ro at present with a cut of tap water every third day. I'm measuring tds, to ensure there is a stable level. This seems to be working so far. I have used this in my last couple of scapes. It's getting 6 pumps od tpn+ daily, with extra iron and some humic acid in the way of NA power.
I'm using good old jbl bottles running at 3 bps at the moment. Running through a atomiser in the inlet.