Mark,
Individual personalities will be added to the fish at a later date, this has been planned from the beginning. When that happens you will see some short chasing and maybe some territorial attitudes from some species, but like you mentioned there won't be any fighting or damaged fish.
In addition, you will also be able to feed the fish and tap on the glass in the future. No fish will die from a result of not feeding them, but it will add your level of interactivity that you mentioned.
There are several other things planned along the same lines, that will add even more functionality to the aquarium, so stay tuned.
