If you have an access to a (large format) solvent printer, I'd recommend the solvent waterslide decal paper. If you don't, the laser waterslide decal paper is the 2nd best option https://drdecalmrhyde.com/shop/laser-waterslide-decal-paper/
And if the colour of the tank is dark, you will have to use white toner/ink printer. If you don't have one, you will have to ask someone else to print for you