No rule for corals. Just make sure you keep adequate spacing between them unless you want to witness them going to war with each other.
Regarding fish, while I know most folks don't like the "inch rules" for stocking, I tend to think somewhere between 3 gallons per inch and 5 gallons per inch is a good reference point. And that's inch of full grown fish... not what they are right now. And as someone already mentioned that rule is really subject to interpretation given that some fish want larger tanks for more running room, and some fish are just plain messy and poop alot. I my opinion, if you go less than 3 gallons per inch, you'd better be on top of everything.