You can remove rock if you want it doesn't truly matter. For example my tank is 75g with a 30g sump it has about 90g of water volume. When I was setting up the tank I read and read you must have 1.5 - 2lbs of rock per gallon and to me this was way over bored. I don't like tanks with a ton of rock in them I think it takes up swimming space for fish and just make the tank look cluttered. So I put 60lbs of rock in it. My rock if very pours and I think this is key more so then a weight requirement. You can haves less rock the more porus the rock is. About a month ago I had an issue where I needed to remove half my rock because of a hydroid issue. I took half the rock out and left about 35-40lbs of rock in the tank. I have had the 35lbs of rock in the 75g for over a month now and I have noticed absolutely no difference in the cycle of the aquarium. My nitrates are the same as they were each week when I do the water change, no fish have been removed or added. I also have no sand bed and run a bare bottom tank.
My stock list includes
2 clowns
Sailfin tang
Midis Blenny
4 chromis
Pajama cardinal
Royal gramma
Marine betta (about 7")
Yellow watchman
Serpent star
Long spine urchin
As you can see my load is probably well stocked. The bacteria we are talking about are microscopic we do not need to provide them with as much room as one may think. They will colonize on everything and some study's suggest that some of the largest colonies of biological filtration happens in the plumbing of the tank because it is dark with very high water flow. My 40g has a snowflake eel and some damsels in it and it only has like 20lbs of rock and it's perfectly fine as well.
You must take into the consideration of the rock you have. I don't think that any true saltwater rock would require more then .75lbs per gallon. I use bulkreefsupply reef savor rock and it's very porus and they also have another rock that's even more porus then the rock I use and very little is needed to sustain a tank. I tend to think about it like this. If you have 100 for a fundrasior people and put them in a school they will spread out in the school but if you put those 100 people in the school gym then they will find a way to fit in the gym same thinkng with bacteria. They don't care if they are touching they don't care if they are cramped. As long as they can feed they will grow and be there.
