Hi Al
I am a couple of pages late with this question, but is adding water to your tank directly from your RO/DI and then mixing the salt in the tank, the best method? I am using "dead" rock and sand also on my 150. I am planning on using two 40 gallon holding tanks, one for fresh RO/DI water and one for mixed salt water, when my settup is finished, but they have been back ordered for weeks, and I am anxious to get water in my tank.
I think I am already doing an even slower build than your "BigAl's Slow 90". I guess that is not necessarily a bad thing. But if your able to tear down a tank and start a new one before I can get mine going, I think I'll have you beat for slooooooooooooooooooooooooow. :rollingey