Unwanted ground collision

[JuhaHo]

[attachment=2200]I wonder what is the main difference between PhysX and non PhysX operators when simulating particles in fluid? PhysX setup is working fine when particles come from separate source, but do not work at all when the system is initially filled. On the latter case, they don't stay inside the liquid. So, I wonder if I should have additional operator to define the buoyancy. On ideal case particles should be floating for a while before getting wet and then they start to travel towards the bottom outlet of the system.

My question is, what non PhysX operator would be suitable for buoyancy in such scenario?