Another nem choice would be a H.Malu, which is in sebae family, but much smaller.
They are also a sand dwellar, which makes it a little easier to control w/ wandering issues.
They are listed as being a little more sensitive compared to a BTA, but all nems will require stable params and an established tank.
They stay around 8" in diameter from my reading on them.
My picassos did take to BTAs, but I, and many other picasso keepers exp loss of black color while being hosted by BTAs for some unexplained reason.