Printers ink is generally thinned with de-natured, I don't know about inkjet ink. The inkjet machine that I have has water soluable ink (HP) not good for a pond. You can get printers ink at Michaels or layout die at a machine tool supply (good luck with that).
Used layout die, or as we called it, Prussian blue in the Nav when rebuilding valves. Stuff sticks like stink on chit. https://www.grainger.com/product/DYKEM-Layout-Fluid-2C945
