As you would expect, as fry get larger, their willingness to expand their range in community tanks will increase.
One of my breeding pairs of Julidochromis dickfeldi resides in a 33g long tank with some other Tanganyikans and various dither fish. The spawning site, which I have posted about before, is at the left end of the tank buried in some holey rock. The pair has spawned a couple of times since I introduced them, but the oldest brood is just now moving out beyond the holey rock.
The older dickfeldi brood, now about two months old and about 5/8 inches in length, have ventured out more than two feet from the spawning site (see photo at top).
In the photo above, I have circled three fry that have moved quite a distance from the spawning site. This only happened within the past several days. They had been keeping to the holey rock near the spawning site.
There are some interesting dynamics with this species. One, the parents will continue to protect the fry until they are about 3/8 – 3/4 inches long. This places a higher burden on the parents because, as the fry move out, the territory to be defended increases. Secondly, as that territory expands, the “safe” areas for the other fish decreases, meaning they stay more bunched up.
Dickfeldi fry much larger than about an inch (at that point they’re juveniles) will become a threat to the newer broods and will thus become targets of the adults. It is not uncommon for me to find a couple of dead juveniles in my species only tanks, which undoubtedly have fallen victim to their own parents protecting the younger brood(s).