Is there a size rule I need to follow?

[butter]

I have a question, i've been thinking of starting a 300 gallon tank. what can I put in there as far as reef safe fishes? Is there a size rule I need to follow? My friend told me I can put as many fish in there as I want and not have any problems as long as the filtration is adaquate enough to handle the bioload. I also want to keep SPS, LPS, Etc.
Thanks
Butter

 

[rcdude1990]

every inch of the fish = 5 gallons