Have been using many products in past tanks with pretty much every UNLS system out there. What in particular that I have noticed is how many people are setting up a ULNS using dead rock. In fact, when I used Zeovit in 2007, user instructions called specifically for "live rock" and dead sand. Now, from a sustainable approach, and some of the bans in the industry, I get it, real "live rock" today is simply mature dry rock. From a micro diversity standpoint, corals get no additional feedings, other than what we put in the tank. This can bring on major algae problems, and in many cases cause starvation for corals, as the nasties simply out compete corals for food. Adding carbon source during these periods could cause cyano, or do I dare say....Dinos. In a mature reef, or at least mature rock, this enables constant food source, as pods, dusters, worms, micro stars, sponges, and obviously many more, sort of balance the water, and I do believe bacteria in turn. In fact, one of my favorite zeo products, sponge power helps to feed those very micro life, that in turn help in keeping water pristine. A well balanced tank, helps to induce spawnings, I love it when stomatella snails spawn, my corals did to, but why did this happen, balance in my opinion.
So to summarize a problem I see, including myself recently, is rushing things, and trying to push cycle quickly, to quickly add fish and corals, only to use products to simulate a mature tank. This would be where I would caution. I also believe that well established tanks meeting most of what agree are signs of a mature stable tank, could stand a much better approach to using these supplements, and programs. Another word, a new tank, should benefit by going through cycling stages, bacteria balancing, and specifically in a situation devoid of life with dead rock. Perhaps installing a micro fauna kit, sourcing sand, and rock rubble from mature reefs, sponges, coraline scrapings, etc. Of course, doing all of this before fish and corals, this is why I emphasize "live rock"/ mature tank. Now, there are some out there that setup using dead rock, push the cycle with bacteria products, quickly add fish and corals, and have success, just wonder if we don't always hear about the fails, as much as the successes. All programs require a different level of daily drops and monitoring, and perhaps many, if they completely studied user guides, and did the research may be turned off by what goes in to what you have achieved with your tank
Cheers