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Roksolid: 43% Silica + many many other beneficial elements for cacti.

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Roksolid is THE BEST slow release fertilizer I have ever used for my cacti. It is a form of rock dust I believe.

For NZ'ers (This site isn't cheap, you can find it cheaper elsewhere but it has all the necessary info):


Constituents of it are:

Analysis of Rok Solid (Averages)

Nitrogen [N] .15%

Phosphorus [P] .8%

Potassium {k} 1.4%

Sulphur .14%

Calcium [Ca] 4.4%

Magnesium [Mg] 5.69%

Sodium [Na] 2.95%

Silica [si] 43.0%

Iron [Fe] 39,000ppm

Manganese [Mn] 1,100ppm

Boron 55ppm

Copper [Cu] 90ppm

Zinc [Zn] 142ppm

Cobalt [Co] 59ppm

Molybdenum [Mo] 2ppm

Selenium [se] 3ppm

Plus many other trace elements.

43% Silica! You HAVE to see how healthy all my cacti and plants are because of this. Silica plays a vital role in cell development and water retention.


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Dude, I would be very cautious with using that with cacti as fine particulates such as powders, especially relatively dense powders, have the tendency to migrate down the soil profile and collect down the bottom of the pot. Imagine pouring sand in a box full of tennis balls, the vast majority of the sand will inevitably end up at the bottom, especially if left in the rain. When dealing with fine materials such as sand and dust this is incredibly dangerous for plants. Due to the size of the particles they practically inhibit gas-exchange in the soil, which not only suffocates roots but also promotes mould and bacteria. This is exacerbated by the fact that the smaller something is, the proportionally greater surface area it has relative to mass, meaning the greater surface tension it has, making the substance adsorp or hold water much more readily than something the same weight but larger grained. Fine dust can take literally weeks to dry out in full sun versus a few hours for coarse sand, if this is at the bottom of your pot it is not at all good. It will form something like a 'densipan', drastically inhibiting drainage and invariably spelling death to your cacti. If you are to use it, I would only add it as a fraction of a percent to the mix.

If you want mineral nutrition for your cacti, try finding some soft volcanic rock like andesite, ignimbrite, cemented ash, they retain their rocky form while quickly weathering to release a wide spectrum of elements.

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Oh! Sweet thanks for the heads up man! Appreciate it!

I haven't heard of those minerals, we're quite limited here in NZ :-/ I'm going to Google them now, thanks!

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