Ok, I'll start with the basics so we are all on the same page. Tank is 65 gals with a 20 gal sump holding approximately 13 gals. of water. T5 lighting, very thin sand bed, less than 3/4" in places, 1 mp10qd, 2 chinese wavemakers, E-shopps skimmer skimming medium wet. Params are generally rock steady at PH 8.0 -8.2, KH 8.5-9, PO4 .06 - .08, NO3 3.0 -5.0,Temp 78 deg. with controller, 2 part dosing with BRS additives. As stated earlier RO/DI is a Spectrapure unit upgraded to 6 stages, 2 pre-filters, 1 sediment cartridge, 2 carbon blocks and 1 DI. I am on a well, incoming TDS is around 354 ppm , after membrane 4 ppm, after DI 0 ppm. I change at 1 ppm. I flush membrane with a bypass for 1 minute before start collecting water from unit. I dose 1 drop of lugols every other day and 2 drops of AF "V"(vitamins) every third day. I run 1/2 cup gfo and 1/2 cup carbon in a reactor. I also run 1 litre of Siporax in a reactor. 7 fish, fed daily frozen mysis. Mix of corals mostly LPS and SPS. Right now SPS down to 6 pcs. frags and mini colony sized. Tenuis are really hard for me to keep if that helps. I have just this past weekend changed the 2nd carbon block rotating #2 into # 1 slot and new block into #2 spot. DI resin changed 30 days ago approx. Incoming well water contains sulfur and black iron, no chloramines.