[Todd]

If you were gonna be mixing dry goods to rodi why not test to see what the ppm is to a 5g mix and then you can eventually work it out so that your top off will slowly add the supps you need to achieve ideal levels.

This is what I am planning on doing, but I would like to make a strong solution, so that the solution will last longer - thus I was curious to how much Mg or CaCl I could add to a solution. Thanks for all of your info, very useful.

there are easier roots like kalk drips, liquid Mg and or calcium carbonate which has some Mg in it

I am going to stick to my plan with mixing dry chemicals with RO/DI water, as it will be very cost effective in the long term and will give me exact control over my Mg, Ca and buffer levels, and will also be very automated once I get it set up.

I may make a thread with my starting levels, what I am dosing, equipment ect. I will be using pharmaceutical grade chemicals (similar to bulk reef supply, or little silvermax's chemicals). I am having a few issues with my Mg test kit (salfart) that I will need to resolve before I start dosing.

Do you have the link to the rest of the article you posted? I would be interested in reading more about particular ions ' dominating the chemistry' as this may change my feeling about dosing Mg in a 1:1 ratio (MgCl to MgSO4).

Todd, I think you'll find the value is temperature dependant, as well as pH, which will vary due to CO2 content. I'd probably just go with Randy's guide..

Ahh, I did not think about this, very good point. However, should the pH and C02 of RO/DI water not be constant though? My understanding of pH is that it is the proportion of free hydrogen ions present in the solution, but this should be constant (ie stable) in 'pure' RO / DI water, should it not?

I think that I will start with Randy's guide and then increase it with the next batch if I feel that I need to get more milage out of the containers.