Just to be clear, it has not been suggested anywhere that the use of live rock in a sump or hang on filter is a problem. The use of biomedia, such as ceramic rings and bioballs is the issue. These artificial biomedia are the source of nitrate and phosphate that need to be eliminated from marine systems. I suspect your husbands aquarium, which mixes both live rock and bioballs, has a massive amount of denitrification taking place within the sump system.
To follow up on my promise to look for a reference, I only had to open "The Marine Aquarium Reference, Systems and Invertebrates" by Martin Moe. I turned to the chapter on Protein Skimming, starting on page 272 in hard back, continuing for 3 pages. Here are some excerpts that apply directly to the concept of filtration in a marine aquarium:
"Proteins and other organics are removed before the are mineralized into nitrogen compounds and other toxins... Note that of all the various filtration capabilities available to the marine aquarist, only protein foam skimming completely removes most organics from the system before they break down."
"Proteins and other organics get into marine aquarium systems through feeding, excretion, adn organic decay. Through the intricate process of biological filtration, these organic substances eventually become nitrates.... Foam separation (protein skimming) removes complex organic substances before they are transformed by the processes of biological filtration."
As a final point in this discussion, I want to talk about the reference made to the book written by Julian Sprung and Charles Delbeck. This is a perfect reference, because each of these experts in our hobby have been advocates against the use of biomedia. I have discussed this concept with Julian Sprung in person. As for Charles Delbeck, he uses ozone and protein skimming as his sole method of filtration. (reference: Coral Magazine, pg. 94, September 2009 edition)