I do. I have the big block in my sump. I have a 120 with no live rock and a large ceramic(not porous)faux rock in my tank. I think it works for me...I've heard about aluminum leaching but, I haven't done a Triton test to know for sure.
I put a box of the spheres in the 10 gallon sump to my 46 gallon DT b/c my nitrates were around 50. It's been 2 weeks now and my salifert test shows a reading between 25 and 50. I have also been carbon dosing vinegar for 3 weeks, so I'm not sure which one is working. I hope to get my nitrates down to 5 or so and stop the vinegar dosing and hope the Marine Pure spheres hold the N down.