Well, I'm using Blur Horizontal + Blur Vertical + another effect (which doesn't seem to be slow) on particles. When the particles move really fast or happen to overlap other particles with other effects, the blur can slow things down.
I read this post by Ashley in a topic about Bloom: "It's not quite what you wanted, but you could try playing around with a combination of blur and glow shaders like this .cap. It's not particularly efficient, though - the blur shaders in Construct are a bit slow."
I was taking this to mean that they could be faster, but from more searching it seems Blur is one of the most intensive shader effects to run and maybe it cannot be written better. Sorry if that is the case. I also noticed that for a full Blur, I have to use Horizontal and Vertical rather than just a single Blur effect. I was thinking this would be slower? I thought with many effects, one effect after another uses the image from the first effect, so it would have more to blur the second time.
Anyway, since what I'm doing is with moving particles, I'd like to save all the performance I can. If it can't be faster, are there any recommended effects that are similar to blur but quicker?
Thanks for the help
Edit: As for the overlapping thing, it was the effects on the other particles that were slowing it down. So yeah, particles with Soften or Blur of anything like that passing by each other are a bad idea (kind of expected). I still have the slowdown with fast moving particles though.