Calcium Supplementation

[Rick]

Rick, check local Petco and Petsmart stores. I have purchased dolomite aquarium substrate from them. It's great for African cichlids.

I purchased a bag of dolomitic limestone yesterday - again in the roughly 3:2 Ca:Mg ratio, but why is that bad? My understanding is that while plants need both, they don't need them equally, making me think that 3:2 is still probably overkill on the Mg.

Thanks Ray, There is a Petsmart nearby I'll try.

Most of what I've seen in the literature is that on a weight basis, plants are using 2-3X the calcium than magnesium, but since the molecular weight of Ca is about 2X that of Mg, they are using Mg at just about the same rate (per molecule) basis.

So I wouldn't mind using some dolomitic limestone with the 3:2 ratio that you've gotten hold of, but I think the higher ratio (Ca) materials are at a minimum a Ca waste or potentially somewhat inhibitive. Especially in combination of common surface/tap waters that may already have a 5:1 Ca/Mg ratio.

 

[Rick]

I was looking up an article from Averyanov on the "dependency" of P emersonia and P hangianum on different types of limestone.

P.emersonia growing on hard crystaline limestone (probably high aragonite, Ca), and P. hangianum growing on soft crumbly stratified limestone (probably yellow dolomite, high Mg).

This article was referenced in an article of Helger Perner who grows P. hangianum successfully in a mix of sphagnum and tree fern (no lime amendments). Which makes another case for my use of baskets of sphag as a good option for growing paphs I guess.

No telling how much Ca or Mg is in Pelger's fertilizer or irrigation water, since I didn't recall seeing any mention of it in the article, but once again it points to the final notion that we probably overdo are emphasis on mineral nutrition (or some are real lucky with their local water supply).

 

[Ray]

The stuff I got is intended for acidic-water neutralization, and is a crushed material that looks like coarse sand. I originally bought it to "mineralize" the RO water feeding my refrigerator - the coffee made with it tastes SO much better than it did with straight RO.

I'll be offering it in 2# bags soon.

 

[Rick]

Looked up this cool article on mineral content of sphagnum

http://www.springerlink.com/content/ktq651w0788v4k74/fulltext.pdf

Two things that pop out is:


The ratio of Ca to Mg is variable based on source ranging from 5:1 to 1.5:1, and

The amount of Ca and Mg (in fact probably most metals) is high enough to not need any external additions from fertilizers provided you get some decomposition of the cell walls.