Yeah, working in the peacock's tank presents problems. They are active day and night, where most of my others close up at night (Thus allowing me to reach in and move stuff, inject hot water into aiptasia,etc...). 3'5"? He's probably a little smaller than that (At least to my eyes, he looked closer to 3") , as Dr. Roy says that folks tend to pver estimate a little). Hydra is a solid 5.5"+...and THICK.
man, that sounded obscene (Just a bit). They really fill out as they grow, whereas I have an almost 4" Chiraga, whose is a lot slimmer than my O. scyllarus. Dagon, my recently passed Peacock was even bigger, and really aggressive, where Hydra is pretty mellow, except at molt time.
-Uriel
PS: On a side note, last night I was on my apartment bulding's back porch, where my neighbors smoke. We were chatting and drinking wine, and I heard Hydra *smack* the tank loudly. One of the girls looked around, like she was trying to see where it came from (It reverberates loudly back there). I said 'Do you know what that is?' One said 'I think it's one of the lights *popping*, maybe from a power surge....' I laughed and told her (They haven't met the mantis shrimp yet, as my room is a bit messy, and they are girls, after all...). They were suprised, but said that it made sense now, especially when it would *pop* repeatedly and rapidly sometimes (Crab feeding day, I assume).