Brood stock tank size

There are many sites that provide minimum tank size for various fish species. When breeding clowns does this apply to the tank size the fish are in or the overall system volume?

I know many people keep clown broodstock in 10 gallon tanks, yet some species are recommended as 40 gallon minimum size tanks.

For example is it ok to keep a maroon pair in a 10 gallon tank if it's part of a 100 gallon system, or does the tank space need to be larger for this larger species?

The size of a broodstock tank will be determined by the needs of the fish. System volume isn't going to make any difference when it comes to housing them. I wouldn't put large clowns like maroons in a 10G, I would go with at least a 20G.

http://www.fishtalpropagations.com/#!home/mainPage
"Making captive breeding easier."

i would say, clowns dont really need large space to feel conformable to breed. actually, relatively smaller space would help encouraging them to breed,(feel safer, have nothing else to do but breed) also save cost.
I had all 20 gal broodstock tanks years ago, but now im happy keeping most pairs in small space.(4~5 gals). my maroon, skunk, clarkii, etc pairs have bit large room around 6.5 gals.
i had a pair of ocellaris i kept them in breeder net (0.5gal) and they happily breed every 11 days.
 

^ depends on the species of clown though. There are some clownfish species that are bred very infrequently, and not ironically, the few who HAVE spawned them, have only done so in very large tanks with anemones.