So much advice I completely disagree within this thread.
Gobies.. there is a limit.. they are not "community" fish as they need a certain amount of space for each of them, or else they will fight to the death. Sure, you can have multiple in a 72G tank, but they have to be far enough apart that they feel another goby isn't invading their space. Sand sifting gobies eat other food and will not die simply by not having enough food in the sand... sand sifting starfish on the other hand will.
Green Chromis are schooling fish and do A LOT better when put in groups. Putting only 1 in the tank is doing that type a fish a disservice.
QT is a good practice for certain fish, but other fish do not tolerate it so it isn't a "must do" rule for everything.
I would recommend avoiding "Dori" in a 72G tank, that is a little too small of a tank for that fish IMO. Only tang I feel suitable for a 72G is one from the bristletooth family, even then a 72 would be bare minimum on size.
You can have about 3 gobies in that size tank without issues, as well as other types of fish that do not have the same look/behavior, like clownfish, angel, etc.
JMO from all my experience.
