thanks for the tips. I pursued the same approach, trying to use a dummy physics object with ellipse collision and setting the blobs to the dummy's position. But I used an id-system and whatever went wrong (can't tell, because I can't find that test cap), the result was that after a few hundred sprites the physics refused to work correctly. Suddenly the framerate went down to under 10fps and objects fell through "solids", etc.
Didn't think of containers. After reading your post, I retried and the container trick works perfectly, as can be seen here:
(Left: custom, Right: ellipse)
Note: The only change is to spawn one dummy with ellipse collision check and one blob sprite, instead of just one blob sprite with custom collision check. Although having double as much sprites, I could double the max particles.
Now I finally have enough fluid to form my game idea to something playable. Yeah
this looks mind blowing O_O