[Delphinus]

Well, now now :D I want a reactor some day .... (hmmm, although, I too would like to move to the Bahamas ... why not have it both ways?? :D :D :D )

Jonathan, don't feel bad, I use tap water too and I have to manually dose to maintain decent Alk and Ca values. It's because you have a lot of stoneys. They do actively pull down the numbers. I find that I have to actively dose buffer to maintain my Alk at 3.7.

The two-part dosing can be a bit of a pain, but what I do like about it is that I can adjust one parameter over the other. I find that with the tap water, I only need to dose Ca at a fraction of what I dose for buffer. But I do have to dose Ca, even with the tap water, on my 75g, on account of the calcium-demanding inhabitants... With the Alk at 3.7 it doesn't take very long for the Ca to go from say 500ppm to 375ppm (I stopped dosing my Ca to see how long it would take, it only took about a week).

I admit to having a RO unit, but all I've used it on so far is my freshwater tank, and for myself :D