Beautiful shellies! Keep an eye on the tetras, these little Tang cichlids can be fierce when breeding. Just curious, what's the tank's water pH and hardness if you know it?
Looks great, Are those Lamp. Brevis. Really colorful little guys. I don't know what your setup is like with the GBR but most tetra's like softer lower ph water. The tetras might be happier with the ram, this guys will probably love the space and high ph/hard water.
I wish I had room to put a 20 long I want to do a shellie tank.