The photo below is a fairly typical example of what I get when I apply
byFormica Fluon markers to a flat surface—dark surfaces expose the hazy film, but you can still clearly see plenty of detail:
You will never get an invisible barrier with Fluon, but you will get a dry film, on which, unlike oils, the ants won't be able to place substrate. If you don't like your application technique, you can wipe it off with a damp cloth and try again. The worst examples I've seen come from overapplication, where the Fluon drips down the sides to form some sordid bukkake hellscape.
Although I haven't tried it, I don't see how Vendayn's suggestion of applying both oil and Fluon could be beneficial, given that Fluon is an aqueous dispersion until the water evaporates away to form the dry film. Last I checked, oil and water separate, and so I certainly don't see how the Fluon can be applied
after the oil, without possibly contaminating/ruining the
Fluon marker applicator tip.
You may have some difficulty with a glass tank configured to open from the front, as there is usually a high tolerance gap for the doors on hinges. You may need to design a custom physical barrier, or simply switch to a more conventional setup. As Serafine mentioned, a lid with a lip, under which the Fluon may be applied (as shown in the above photo), works best. Although Fluon will work on glass, it works best on virgin, high-gloss plastics.
Edited by drtrmiller, December 13 2016 - 9:15 AM.