I don't have a lot of demanding corals right now. My alk has stayed at 8 for a long time. I've hesitated to start dosing because that is essentially what they recommend as the titration point. I used a 60G as my refugium (because I had it sitting around), which flows into my sump (about 30G). So my downstairs volume is about the same as the DT. I think that consequence of that has been a lower concentration of nutrients to worry about in the refugium (ie slower chaeto growth) and a lower consumption of CA in the DT. So far all of the regular water parameters have stayed rock solid low... So I'm waiting.
I'm at a flow rate of about 510. It is my first basement sump. I went on the advice of someone to use a 3/4" return pipe... At the time, it matched the pump. That turned out to be very inadequate. So I will be repiping up to the floor joists to reduce head loss. I'm also going to gravity feed the pump so that it is more of a straight shot upward on the return side. That process requires me to have the sump drilled. Figuring out this piece of the puzzle was more difficult than I anticipated. If I didn't have the Neptune flow rate sensor -- I wouldn't even know where I'm at. I've thought about just leaving it at 510GPH. That said, I think the pump will be more efficient with the straight shot. With any luck, that will reduce the head loss enough so that I can back off on the pump and reduce its power consumption. I've been trying to avoid using an AC pump. I don't think you could hit your flow rate with a DC pump without using 2 of them. I'll let you know when I get the Sicce in place in the modified plumbing condition.