Naphthalene/mothball in diesel tank as diesel bug prevention?

[Halo]

I thought Grotamar was impossible to get now ? If it is available again a link would be much appreciated !
(Sorry about the hijack Vas !)

Officially it’s for commercial use only which I find reassuring as to its effectiveness. I got a 1 litre bottle last month on eBay from Germany. Oily bits also sell it in large cans to other businesses but the cost is very high.