I stumbled upon a missing fluid texture. Posted the same on the forestry issue tracker.

From left to right you see lava, forestry biomass and forestry honey. The biomass gets rendered correctly, the honey not. Through the BC Fluid pipes the honey renders correctly.

I don't know on which end this issue is. Noticed exactly the same in railcraft tanks. So probably forestry?

Picture:

Sorry, noticed that I should post this in the BC Forum. Its posted there now