Tried to edit to clarify, but I don't think I have that option. Here's an example to illustrate what I am trying to ask:
Say I have a 250 gallon tank. I want to stock it with 25 inches of fish (1 black & white ocellaris clownfish, 1 Scott's fairy wrasse, 1 jawfish, 1 Bartlett's anthias, and 1 Achilles tang). Using the 1 inch per 5 gallons rule of thumb, I have used up 125 gallons.
I would also at some point want to add an anemone and a few corals. The max size of the anemone is 20 inches. Would I use the 1 inch per 5 gallons rule of thumb for the anemone? That would use up another 100 gallons, leaving me with 25 gallons left for the coral and clean-up crew, and I have no idea what rule of thumb applies to the clean-up crew or corals. For example, if I add a 12 inch starfish, would that use up 60 gallons of my total? Or would it be less since it's both removing and creating waste?