I have a collision object with the fluid particle emitter inside. The idea is that when the fluid fills up the object, it explodes and all the particles falls out.
The problem is that I can't find a way on how to animate the collision itself and turn off the modifier on certain frame?
Typically you can animate any value in blender by hitting i. If there isn't an on/off switch, you can modify the collision object's geometry.
Go to the frame before the shattering. There hit i > Scale. Go to the next frame and sto scale the object up. Make it so big that it doesn't block the flow of the fluid. i > Scale again to save the size.
Now it should work.
