I am just curious about what the role calcium has in a planted tank since I've seen it mentioned a few times and I don't know why it is added or by what method (for example, do you use calcium carbonate, calcium chloride, calcium nitrate, or what. And why?).
CaCl2= maybe for marine tank to booster Ca++ levels. CaCO3, mostly to increase KH, but also to add both Ca and KH. CaCl2 dissolved very easily, CaCO3 is very slow and tough to dissolve. Ca(NO3)2 is eas y to dissolve and good where you have N and very soft water, RO or to dose to a marine planted tank.
I have yet to see a singe documented, verified case of Ca++ limitation in natural or in planted aquariums.
I've been using marine salt as a reconstitution of pure RO water for more than 10 years without any issues. I've had a number of fish spawn in this water, including Pelvicachromis pulcher, Mikrogeophagus ramirezi, Otocinclus, CRS shrimp, rasbora, danios of various types, white clouds, guppies (of course...I think that they will reproduce in used motor oil
). And I'm currently raising daphnia in another tank in harder, green water, but using the same salt for reconstitution.
GH booster is generally cheaper.
You might add 3 tsp a week in the 125 Gal.
I used the Kent Marine salt for two reasons (I'm not using pure NaCl). One, it was Kent RO Right for which I was substituting with the salt. Two, I was using the Kent Marine salt for my reef tank so I had some laying around. I haven't tried any other salt mixes. The salt I have now is years old (though very dry and doesn't appear to have degraded. I was told by my LFS that this brand is not what it once was since the company that made it was taken over by another company. I won't name names because I have no proof that the salt has dropped in quality.
GH booster can be had from various DIY dry salts vendors on line.
As far as using RO, fine for your reef tank there........but the tap is okay for plants, at least you can blend with RO also. This will save you massive time, energy messing with the water changes.
I lived in Davis and the water is rock hard deep well water.......the oil/ag stuff is minor, the drinking/cooking water is where you should spend time using RO, the plants mitigate most of the issues. KH for some fish might be your only variable you may wish to adjust, baking soda does that trick easily.