I have at last found the Holy Grail, a balance that has produced no N03 and no P04. Anybody that helped me late last year, thank you. Even on a low range N03 test the level was less than 1ppm and no water changes have been made in 4 weeks only top ups. Hard corals are growing at a high rate as are xenia populations which are covering the tank walls. The answers were all in the refugium, the balance of live sand depth, water flow rate and caulerpa growth.