Vortech help/thoughts

[parkinsn]

So I want to put my vortechs on the back of my tank. Here is the issue, I have a piece of black acrylic on the back of my tank with a small air gap between it and the glass due to the silicone holding it on. Without draining the tank and drilling holes in the acrylic for the wet side to sit in, do you think its ok to put them on the acrylic and compensate on the dry side for the thickness of glass, acrylic and air?