Bellrings (tundra fort) has just brought up magma 45 z-levels to fill a moat. 90 pumps double stacked, all components made of iron including the blocks. I thought I had over-engineered my pump stack, I needed 7 standard water reactors to get it going but I was glad of it in the end. Filled a 4-wide moat around the outer perimeter of a 4x4 embark in less than a season, with the ability to pull up more whenever I want it. Also oddly I really didn't suffer noticeable lag while doing it, despite the multiple reactors and massive amount of liquid moved. Maybe because it was a double stack with 2 draw tiles per level?
Now to tap into the supply and get me some above-ground magma forges/glass furnaces...