Ok this is a waist of time unless we know what size your tank is, weather you have a sand bed or not and how much live rock you have. Also you will need to tell us how long this has all been together and if it is finished cycling or not.
reason being if you just finished cycling a 20 gal tank with 5 lbs of LR and a sand bed you can add a lot more than a 20 gal tank that has nothing else, on the same token a 90 gal tank with 180Lbs of well cured LR will handle almost any bio mass you can reasonably throw at it.
the old 1 fish per month rule and such were created with freshwater tanks that are new and have a thin layer of coarse smooth rock which means the water column is going to be supporting the majority of the bacteria that break down ammonia and nitrite.
in a reef tank with live rock that has finished the initial cycling the initial population of bacteria will be immensely larger than a tank with no liver rock and sense Bacteria doubles when it multiplies it can adjust faster.
for a stupid example take a 20 gal tank that just has water in it, for arguments sake lets say it has 5 bacteria and that the reproduction rate of the bacteria is it doubles every day, so day 2 you have 10, day 3 you have 20, day 4 you have 40, and day 5 you have 80 little bacteria.
so lets compare this to a 20 gal tank that has 30lbs of live rock and for arguments sake well say the rock supports 100 bacteria with the water initially, well day 2 you have 200, day 3 you have 400, day 4 you have 800, and day 5 you have 1600 little guys
so you can see because the second tank can produce bacteria faster it will be able to support a larger initial addition of bio mass.
oh and for the record the numbers I used for the bacteria are a little low but I am not digging out my book and trying to figure out what the sustainable density per gal is
