Dr Ron,
An update on the c. varians (flatworm eating slugs) that were added to my 180. After acclimating them in the sump and confirming they were healthy (and letting them dine there in the interim) both slugs were added to the main tank. I never saw more than one at a time, leading me to believe that A)they took turns being out and about or B) one perished. Based on their speed it appears a 180 can support one (or is it two) for an indeterminate period of time. It eats flatworms, but not at a pace that puts the population at risk of complete extermination.
They are also escape artists. The one that has been visible went from the main tank, through the overflow, through the 3/16" holes in the screen. down the standpipe, past the skimmer intake, over-under-over the baffles, and back into the insump refugium, all in less than eight hours. It was considering a trip through the return pump when I found it
It's living in a water park
.
Now that I think about it there may be a reason the skimmer overflowed recently. All powerheads and pump inlets are now covered with sponge prefilters
Agu