yeah, attackfish, i think adding more dats may help. but i also found that the structures can help stabalize them also. i bought my first dat, and didnt have money for the others, so i bought them every few weeks one by one. My first one however, was even stable by himself . . . and i believe that if there is a structure they like and want to protect they will stabalize. Do you have big driftwood? I had bigger driftwood in before, and they LOVED it, and it looked very natural also.
thanks for all the other responses! my 55g is a broke mans monster tank haha!