When I started my fifteen gallon tank, I decided to do a fish-in cycle. I couldn't source enough lava rock, so I only planted on one side.
With the half-planted tank, I let it run for a month before adding my first five ember tetras. Of course, they were watched, like a hawk, and water was tested daily. After a week, four more were added. I floated the bag of new fish and did something else, for a while. When I went back, to add tank water to the bag, I found both groups of fish with their noses pressed against the plastic barrier. A week later, four more were added; with the same behavior shown.
Next, came the three otocinclus. I acclimated them and released them into the tank. The little embers swam with the otos, from the very beginning. They were welcomed without any fuss; even though they were much larger.
Then, I added five shrimp. When they were released, the embers all ran and hid. It took them two or three days to get over their fear of the strange, scary monsters.
Lots of fun!