Wet/Dry questions

The sump on my 90 is a 2'x1' wet/dry with a water level of 7 1/2". I replaced the bio ball chamber with LR, so I have a trickle over live rock, then underneath that a chamber of empty water that flows into the other half with the skimmer and pumps. 2 questions. 1. What's the difference between a wet/dry and a sump? Is a wet/dry just a form of sump? 2. Is there anything that could live down there, or would the noise be too stressful? I was thinking about adding a Debelius Reef Lobster (Purple Lobster), but I didn't know if it would be too small/noisy. Would it need more space? Other suggestions of of relatively big cool invert for the sump? Also, I like the idea of a lobster because he would eat meaty chunks of food that got away from the coral and fish and went over the overflow during feedings. A lot of this stuff gets trapped in the chamber of water underneath the live rock trickle. If I got one of these guys I would drop the Live Rock down to the sump floor so he'd have caves like they like. Oh, and also, would the fact that its dark almost all the time be a problem? I thought no because they are nocturnal and they hide in dark caves during the day anyway, but I thought I'd bring it up.

 

A Wet/Dry works by allowing benificial bacteria to grow on the bio balls/bale. a reef usually dosnt need such colonies to grow and therefore dosnt need the balls/bale. As far as i have read, this is the only difference in purpose between a wet/dry and a sump. As far as your second question, i dont know...not enough experience with lobsters to say.

 

Most wet/dry (sumps) come with a drip tray over the bio balls. Filter padding is put in the drip tray to catch any large detritus.