I'm sorry- I looked at the previous two pages of this thread, but where is the splashing coming from? If it is from your return, then I would add a filter sock. However, the mist has me puzzled. Splashing normally doesn't cause a mist, but possibly hundreds/thousands of microbubbles popping?
It would be easier if I had a full sump pic. Do you have one? Also- can you capture what the mist looks like, or can you detect what side of the sump it's coming from?
125 gal. reef w sump/refugium & 8-bulb 640w T5's
45 gal fresh w/plants + CPF lighting