Agrocrete / man made LR

[kbd635]

Well, where to begin...... ?
I emigrated from Scotland a couple of years ago and brought my tank with me.
My tank is still in the "re-planning" stage, as I need to buy all new electrics (240V in UK), so I'm actually thinking of making my own LR. (not all of it obviously.... lol)
I have the crushed coral sand from my tank, which I have seived to separate the big stuff out and I'm toying with the idea of making some structures using portland cement, softener salt (big grain stuff) and the bigger coral crush (it's about 5mm x 3mm ish).
I have some of those "green" packing peanuts which dissolve in water, so I think I'll use them to create some rock with some bigger holes for critters and higher surface area.
I was intending to just put it in the rain butt and let the rain from the roof flush it out, but that won't work til spring. lol
Any advice / links would be helpful?
K