Incorrectly displays a 6 slot interface instead of a 9 slot. This commit: PrototypeTrousers/Applied-Energistics-2@de324aa where they renamed the texture for 9-slot interfaces means that it is now possible to create a new texture for PAE2's 9 slot fluid interfaces.

Oh, i dont see that update. my bad

Sure.

I mean, do I just save the file as interfacefluidextendedlife.png?

Replace this assets/appliedenergistics2/textures/guis/interfacefluid.png

But they renamed the PAE2 9-slot interface to a different texture? (As per my previous comment)

Here temporary solution

How can I use that?

Yeah, you should be able to add it to the resource pack, and it will work for new PAE2 versions. At the moment, I believe a replacement of the file is still needed, but just add it for the future, under interfacefluidextendedlife.png.

#259 should fix this issue