fish is relatively high in fluorine, but it turns out that seaweed and algae is very high in fluorine, high enough that this might solve my problem.

this study presents the fluoride content of spirulina as a danger, but if the concentration is 60 mg/kg, and i need 4 mg, i only need 1000/(60/4) = 67 g of the stuff. and, that is almost the same concentration as toothpaste, in an actual food source. if i decide i want to get 1.5 in each bowl, 1000/(60/1.5) = 25 g. that's the size of a large strawberry. that's workable..

https://www.researchgate.net/publication/343635156_Fluoride_content_in_dietary_supplements_of_spirulina_Kaldunska_FLUORIDE_CONTENT_IN_DIETARY_SUPPLEMENTS_OF_SPIRULINA_ARTHROSPIRA_SPP_FROM_CONVENTIONAL_AND_ORGANIC_CULTIVATION/download

that means that the algal oil should have some fluoride in it, alhough it might be a struggle to have it measured

so, i'm starting to work this out.

i can probably get 20-30% from the water, at least. if i'm lucky, i can get another 20-30% from the algal oil and maybe another 20-30% from spirulina or chlorella. and, then i can get extra bits from spices & from anchovies.

i just need to add it up.