Tank Mate

[Gonodactylus]

With enough cover and places to hide, it might work for weeks or months, but there is a risk. I've seen a 6 inch O. scyllarus take out an 8 inch clown trigger. There is also a risk to the mantis shrimp. Generally, I would not recommend keeping to large predators in the same tank.

As for aggression in males and females, no difference. There is far more variation with changes in the molt cycle than you will see with sex differences.

Roy

[Scotty]

wow

[Scotty]

Disregard the last 'wow', i was testing my system and it got away from me.
I've had a lot of mantis in a lot of different 'compatibility tests' and here's my 2 cents. The reef is fine insomuch as the mantis will not eat any thing important,(snails, crabs etc. will be devoured) although during the molt cycle, a big mantis can and will move around a lot of your scenery, kick up a good sand storm and eventually dig in places you won't want him diggin. How big is the reef anyway?The bigger the better.
The issue with the grouper, seems to me to be, how large is the tank? The bigger the better... I would say 15 gals minimum. And keeep them both well fed. Gonodactylus is right, but for myself, I have had many mantis (I consider myself an old school stomatopodder) and I have had little problem with peacocks bunking with fish. I would be more worried about the groupers instincts to eat crustaceans. How well do you know this grouper?
Ultimately, this is a problem with your girlfriend, you obviously need more aquariums and she must learn to deal. :-)

[word]

scotty, i love it when you post that pic!