Cancer Can Be Treated By Calcium Carbonate

[Elephanto]

If it is a matter of alkalinity, it would support Peat's claim that alkaline minerals are interchangeable and keeping an overall high intake matters more. I think Magnesium is more effective if it's of fungal origin, because Calcium can actually promote biofilm formation:
Discovery of Calcium as a Biofilm-Promoting Signal for Vibrio fischeri Reveals New Phenotypes and Underlying Regulatory Complexity. - PubMed - NCBI

Using a calcium chelator limits biofilm formation :

EGTA also limited biofilm formation in minimal medium with glucose as a carbon source (not shown) and in 1:10 strength LB. This effect of the chelator was compensated for by addition of excess CaCl2

Calcium Causes Multimerization of the Large Adhesin LapF and Modulates Biofilm Formation by Pseudomonas putida

Whereas Magnesium is only anti-bacterial and anti-biofilm, and Mag deficiency is an important enabler of biofilm formation.
Magnesium Limitation Is an Environmental Trigger of the Pseudomonas aeruginosa Biofilm Lifestyle

 

[Amazoniac]

If it is a matter of alkalinity, it would support Peat's claim that alkaline minerals are interchangeable and keeping an overall high intake matters more. I think Magnesium is more effective if it's of fungal origin, because Calcium can actually promote biofilm formation:
Discovery of Calcium as a Biofilm-Promoting Signal for Vibrio fischeri Reveals New Phenotypes and Underlying Regulatory Complexity. - PubMed - NCBI

Using a calcium chelator limits biofilm formation :

Calcium Causes Multimerization of the Large Adhesin LapF and Modulates Biofilm Formation by Pseudomonas putida

Whereas Magnesium is only anti-bacterial and anti-biofilm, and Mag deficiency is an important enabler of biofilm formation.
Magnesium Limitation Is an Environmental Trigger of the Pseudomonas aeruginosa Biofilm Lifestyle

Various microbes thrive on magnesium, so much so that from your last link it appears that this is one of the reasons why when they're deprived of it, they switch to hybernation protected by these films, which happen to contain magnesium in their structure:

The biofilm matrix destabilizers, EDTA and DNaseI, enhance the susceptibility of nontypeable Hemophilus influenzae biofilms to treatment with ampicillin and ciprofloxacin

"Many studies have demonstrated the roles of calcium, magnesium, and iron divalent cations in promoting cell growth and cell-to-cell adhesion in biofilms. Divalent cations appear to stabilize the biofilm matrix of a variety of organisms by enhancing structural integrity through electrostatic interactions that serve to cross-link the matrix. Divalent cations have also been shown to enhance the interaction of a mucoid strain of Pseudomonas aeruginosa with tracheal epithelium (Marcus et al. 1989). In some bacteria, divalent cations also enhance EPS production. For example, mutations in the magnesium up-take system of Aeromonas hydrophilia cause a reduction of biofilm formation and swarming motility (Merino et al. 2001) and divalent cations, in particular Mg2+, were found to greatly enhance EPS production by Staphylococcus epidermidis strains (Ozerdem Akpolat et al. 2003). In contrast, in the presence of the cation chelator ethylenediaminetetra-acetic acid (EDTA), EPS production by S. epidermidis was significantly reduced (Ozerdem Akpolat et al. 2003). As divalent cations also contribute to the integrity and stability of the outer membrane of Gram-negative bacteria (Leive and Kollin 1967; Geesey et al. 2000), EDTA likely exerts antimicrobial activity by chelating cations necessary for growth and membrane stability and may also display anti-biofilm activity by reducing EPS production and/or enhancing the detachment of bacterial cells from the biofilm (Banin et al. 2006)."​

Their virulence can be increased with more magnesium.

There's the absorption region issue as well:

Magnesium in man <feminist taking off her bra in protest>: implications for health and disease

"Mg2plus is poorly absorbed in the duodenum, where unfavorable electrochemical gradients may even result in a limited amount of paracellular Mg2plus excretion (389). In more distal parts of the small intestine, such as late jejunum and ileum, the driving force for passive Mg2plus transport is established by the high luminal Mg2plus concentration and the lumen-positive transepithelial voltage of ~15 mV (164)."​

But it doesn't make sense to deprive yourself of it because you'll create way more problems for you than for them. What you can does it to fawor more absorbable forms and smaller amounts at a time to minimize waste. Magnesium acetate/malate can be interesting because these ligands might help in solubizing the films if they follow magnesium to its absorption site, not sure.

Temporary Strict Iron Avoidance And Its Potential Advantages

 

[Elephanto]

@Amazoniac Thanks for the correction. I've seen so many studies showing Mag having anti-bacterial effects that I figured it couldn't have the opposite effect in a different context. But in a realistic context regarding Mag intake and body's levels, low levels of Magnesium only enable and potentiate the damage of Endotoxins. See another study showing it :

These observed significant elevations in plasma LPS in Mg deficient rats indicated that prolonged Mg deficiency results in increased intestinal permeability to bacterial products leading to increased circulating LPS, along with elevated endotoxin receptor expression in the heart; this CD14 elevation may further amplify the cardiomyopathy leading to eventual contractile dysfunction.

The Role of Magnesium Deficiency in Cardiovascular and Intestinal Inflammation
So even disregarding the other negative effects of Mag deprivation, it is not an effective strategy to limit bacterial overgrowth.