haven't set up myself yet, wondering if anyone has results?

I have done something similar. I used an old Aquaclear 70 filter and put in a bag of aragonite. I have the filter hanging on my top up resivoir. It buffers the water just fine, I doubt if there is enough top up water going in the DT to keep calcium levels up.

My RO/DI water is "0" TDS
Tap water is 13 TDS some times 15 TDS when its raining.
Tap water Ph 8.5 but as soon as in the glass and as soon as i start swirling the Ph probe the Ph goes down to 7.0 in 30 seconds.

RO/DI water Ph is 9.0(!) but with the same almost instant Ph drop down to 6.9 after ph probe swirling in the glass.

Did anyone else tested their RO/DI water Ph?
Or even better Ph INSIDE the water filter?

ok, noob question here: Isn't the idea of a RO/DI filter to get something as close to pure H20 as possible so that you can add salt to it to get 'seawater' which contains all these elements -but nothing else ?

In other words, doesn't the SALT add all the necessary trace elements ?

no.

You'll find many salts if mixed as to their directions will get less than optimal levels of Ca and Mg to start. Plus corals like SPS will suck the Ca and alk out of the water column, reason people use CA reactors, kalk or dosing (manual or automatic).

I find that odd. Considering that reef salt is a very application-specific product, why don't they put appropriate amounts of Ca & Mg into the product then push frequent water changes ?

Just seems like a simple and efficient way of doing it.

what should be and what is can be a little different. Many posts on supplementing.

What unit of measure is your TDS reading, certainly not PPM.

When you refer to the "PH drop", I doubt if the PH is changing that rapidly, most likely it is the PH probe stabilizing. Think about it for a second, PH changing from 8.5 to 7 in 30 seconds without any additives is virtually impossible.

I think TDS (Total Dissolved Solids) is measured in PPM (Parts Per Million):smile:

I know how TDS is measured, I've never heard of 13 to 15 ppm out of a tap.