I'm not a materials scientist either, I am a software engineer, but what I do know of it suggests that Mike is probably correct
https://www.lenntech.com/periodic/water/aluminium/aluminum-and-water.htm
> Aluminum metal rapidly develops a thin layer of aluminum oxide of a few millimeters that prevents the metal from reacting with water.
> The most abundant aluminum compounds are aluminum oxide and aluminum hydroxide, and these are water insoluble.
> At pH values below 4.5 solubility rapidly increases
As for bauxite, bauxite is a sedimentary rock composed of aluminum minerals such as gibbsite, boehmite, and diaspore, which are also all considered water insoluble except under extreme conditions: high temperature combined with the presence of strong acids or bases, which are very far from the conditions normally found in the oceans or aquariums
likewise, we can easily find sources corroborating the claim that aluminum oxide, bauxite, and a number of other elements, can interfere with the free aluminum readings on an ICP test:
https://www.osti.gov/etdeweb/biblio/20470534https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1751-908X.2015.00356.xhttps://www.osti.gov/etdeweb/biblio/21582747
while he didn't say it in the most gentle or friendly way, I think he actually had a good point: as laypeople it can be very easy to be misled by laboratory-grade scientific equipment when we don't sufficiently know the intricacies of how to properly use it. Effectively using laboratory-grade test equiment means obtaining enough knowledge and relevant training to be able to identify things like confounding factors, interferences, as well as building experience with that particular device well enough to properly interpret the results, and without all of that it can be very easy to look at a number on a test readout and get scared