I've found the problem. All three MIA chromises made it into the overflow and down into the sump. Of course, I couldn't see them because they went directly into an acrylic box that I made to house the carbon for a modified Hiatte system.

Now, I have a fire fish missing, though. I bought 2 of them when I got the chromises. I've found one of them in his hiding spot under a rock. Can't find the other one, though. It's not in the sump or caught in the plumbing 'cause I took it all apart when I found the chromises. Hopefully he'll be out tomorrow at feeding time!