ok but i went to a garden center today and they had a tank with about 5 in and it muct have been a 200 litre and they were all in good condition and i asked if they fought or injured each other and he told me there was no problems with them
you have to remember that things in shops do not stay that way for the life of the fish/lobster etc
they are in there for a very short time. it may well work for a short time but as the lobsters get older they will become more and more aggressive
well,,,i had at 1 point 3 in my tank,,they had their own space and didnt fight often,,,if they did it was over food,,,id say 2 wud be fine aslong as u have plenty of places for them to hide..