I have a sal in a 135 ca/sa community, smallest one in there. At first when it was heavily decorated, he would guard his little home and chase anything that came near, no matter the size. Now that I've taken 80% of the decor out, he's great.. For they're size, they can pull an attitude, but nothing serious to worry about.. As far as a pair, if you get a m/f, you might have problems for others if they breed down the line. M/m might have problems between the 2. I say if your going for another fish in a community, 1 is perfect.