Hi i just noticed a major problem, or a bug if u might call it while working with fluids. I noticed that fluids arent very reflection friendly, especially fluid clouds. If you happen to have a reflective surface around a fluid object you will most certainly get thin black lines all over your ref object and these lines are more prominent in an animation.
To solve this issue you have to composite the reflection of the fluids over your 'shiny' object.
For example i had a highly reflective chrome object flying above a fluid cloud.After a 100 frame raytraced render i noticed these thin lines running all across my render from top to bottom.They werent an aliasing problem as i re rendered a single frame with the aliasing settings maxed out to ridiculous proportions, still , no joy.Then i realized that its a fluid reflection problem and my only workaround was to assign a background shader to my ref object that caught the fluid clouds reflection which i later had to composite.
Since a alot of people are talking about fluids on this forum i thought this would be useful information just in case any of you do run into this problem.Use the above solution.