The pot should be removed as should the 'stuff' around the roots. I find a dressmaking pin useful for removing all the 'stuff' from the crevices between the roots.
If the roots are spread out and buried in the substrate that should be enough. But sometimes plants arrive with trimmed roots. If the plant won't stay in the substrate, a few pebbles around the stem should hold the plant secure until it has grow enough root system to stay there once the pebbles are removed.
Plants such as Java fern and anubias need to be attached to decor. They have 3 parts - leaves, thin roots and a thick root-like rhizome which has the leaves growing out of one side and the roots from the opposite side. The roots should be spread out across the decor and the rhizome can be held tightly with sewing thread, or fishing line or even a zip tie. Or it can be glued using cyanoacrylate superglue, no other type of glue. I tie mine with sewing thread but members who use glue report the gel type is better as it stays where you put it, but runs from the liquid type go white when under water. These plants soon attach themselves to the decor like ivy does to a building.
If the roots are spread out and buried in the substrate that should be enough. But sometimes plants arrive with trimmed roots. If the plant won't stay in the substrate, a few pebbles around the stem should hold the plant secure until it has grow enough root system to stay there once the pebbles are removed.
Plants such as Java fern and anubias need to be attached to decor. They have 3 parts - leaves, thin roots and a thick root-like rhizome which has the leaves growing out of one side and the roots from the opposite side. The roots should be spread out across the decor and the rhizome can be held tightly with sewing thread, or fishing line or even a zip tie. Or it can be glued using cyanoacrylate superglue, no other type of glue. I tie mine with sewing thread but members who use glue report the gel type is better as it stays where you put it, but runs from the liquid type go white when under water. These plants soon attach themselves to the decor like ivy does to a building.
You might keep running into aggression issues until your group is large enough - they need a pecking order to spread out the aggression, as you get more in the tank make sure you add them in bigger groups too. I'd try getting to 10-12 quite soon and then add a few others to get to about 15-18 fish. 
I demand a full tank photo....please 
