Adding the last post to this thread (finally) so that someone else may be able to benefit from the experience and we can all learn from each other's successes and failures (thanks for reminding me, D).
All three are gone.
I gave one to a reliable, reef-keeping friend and one week after he got it, he found it dead. I don't know if it was the change in water chemistry, his water quality, his feeding habits, etc. but I now regret giving one away. (A Mother's guilt).
I had my remaining two, one living in a 14 gallon biocube and one in a 20 gallon tank. They were doing well and still only eating live fiddler crabs but I was trying new foods on a regular basis. They were pretty reclusive.... much more so than when I had them in breeder nets, but perhaps that's because they didn't have much room to escape in the breeder nets. Two or three times a day I would search all the rockwork until I spotted them and would wave some food near them but they never took it.... they just kept watiing for me to leave and they'd then chomp a fiddler and leave me the shells to clean up.
One day in early July I went down to feed the fella in the 20 gallon and found him out in the open and looking kinda pale and listless. I checked the water parameters and everything was the same so I offered him food and then left him alone. When I got home from work that day, he was dead.
I checked the water again, siphoned up the barebottom of any debris, rearranged a few rocks, and left the tank running.... I was in mourning and denial. A few days later I got the brainstorm to move the guy in the 14 gallon tank over to the bigger, empty tank so that he could enjoy more space. 3 days later, he was dead.
I wracked my brain and re-played everything over and over in my head and the only two things I can come up with are:
The water was too warm? The July heat had kicked in but I wasn't running the AC much during the day so it was probably getting to about 75 degrees in the house until I got home and flipped on the AC. Could the warmer air temperature (and ultimately the warmer water temperature) have killed them? Maybe the octo in the biocube wasn't as affected by the heat in the room since the biocubes are so closed off?
My other theory is that something was in one of the live rocks that killed them. I was only giving them small fiddler crabs that they could easily conquer, but perhaps one of them hid in one of the rocks for a few months and grew big enough to actually kill the octos?
Unfortunately I'll never know and probably will never stop wondering what I could have done differently but I guess we all go through that. It's just odd that they were both fine and then I lost them in the same week, in that same tank. I had the pleasure of their company for a little over 4 months but feel like I was robbed of the 12 months I had hoped for. I'm sure someday I will try again.
Sue