| | Re: First natural tank
I would just get the tank going and see if you have problems down the line and worry about it then.
For later, check out the fertilizer section in the forums. There are some stickies of what different holes, coloration, and deformities can indicate.
Check out your tap water details. The city or water company should release a water report about once a year or more. It will have details on Mg, K, Ca,..... I found it helpful.
I' not sure about pure calcium carbonate, as I haven't used it. I have used crushed corral (which I guess is mostly calcium carbonate) and in my case the little I had under the soil didn't break down fast enough to keep up with the plants demands. The tank was very packs and vals seem to need a little extra calcium. Seachem equilibrium or Tom Barr's GH booster helped out for me.