Tourmaline Mineral Balls have been used for water purification for decades as they add mineral content back into water, They have also been used for therapeutically uses like bathing.
These Mineral Balls hold a slight negative charge which can absorb impurities in the water such as ammonia and nitrates and have been used to treat and purify tap water.
I personally use them because they are abundant in minerals which I will list below which does help with shrimps biological functions.
I cant emphasize this enough, young shrimp especially need minerals just to survive molting, there is mineral removal and absorption happening when a shrimp molts lack of anything and a shrimp might produce a thick shell or a thin shell, the shrimp might not produce enough molting fluid to help remove the old shell, chances are if you are not seeing many baby shrimp they are 1.lacking in minerals or 2 lacking in nutrition.
Adachiite, Bosiite, Chromium dravite,Chromo Almino Povondraite, Darrellheryite, Dravite, Elbaite, Ferufite, Fluor Buergerite, Fluor Dravite, Fluor-elbaite, Fluor-liddicoatite, Fluor-schorl, , Fluor-tsilaisite, Fluor-uvite, Foitite, Lucchesiite, Luinaite, Magnesio Foitit, Maruyamaite, Olenite, Oxy chromium dravite, Oxy dravitr, Oxy Schorl, Oxy vanadium dravite, Povondrite, Rossmanite, Schol, Tsilaaisite, Uvite,Vanadio oxy chromium dravite, Vanadio oxy dravite.
The very short answer in no because I can't prove they actually do anything but I do think they do something..Think of it like this if you are missing one single element you could be potentially sick or feel miserable, this way you cover your bases.
I also like the way they look in a tank and I am pretty sure bacteria and other things like algae grow on them for the shrimp to feed from.
I like to use 2-3 Tourmaline Mineral Balls in each tank every 6 months to a year.