My name is Howard and I'm a marine plant enthusiast. A few of you folks have some interesting notions on plants.
Phosphate is essential to plant growth (to all life), but itââ"šÂ¬Ã¢"žÂ¢s not the primary fuel. If you don't consider C, N (as ammonium, nitrate, and nitrite) is the primary fuel for most plant growth and IMO is usually the limiting nutrient in my tank and most tanks. There are fixers that can take up atmospheric N when there is an abundance of P, but the plants we usually consider chronic problems in reef tanks - ex: Valonia, Asparagopsis, Caulerpa peltata - aren't fixers. IF there is an abundance of P in a brightly lit, well circulated tank, IMO you will see it expressed by the presence of plants that can make use of it - probably a gelatinous-type mat-forming cyanobacteria.
Also, putting many algae in the dark won't kill them, as some of you think. The obvious plant dies but it persists in a dormant form for a long time. IMO if you've ever had Derbersia or Asparagopsis in your tank, you are always going to have it even though it may not be apparent, waiting for the right conditions to bloom.
I'm curious what the people who are putting their rock in the dark think of boiling rock, or otherwise sanitizing the rock such as in a vat where ozone is injected. A prominent reefer here in the Puget Sound, who had a RTOTM on RC, appears to be advocating this on Reef Frontiers and people are doing it. The rock boilers seem to have the same premises as the rock cookers, but have reached a different conclusion on the most effective way to deal with a substrate they feel is saturated with P.
If you are trying to limit P input to the tank and control some types of plants in the tank, why are you putting reef rubble in your tank? Why not use a synthetic media for a rock substrate? That seems to me to be the most logical path to where you want to go, instead of putting live rock in the dark or boiling it? There are a number of porous substrates with very fine pore size.
The title of this thread is a bit odd. What's dangerous about putting rock in the dark? Pressurized bottles of CO2 is certainly dangerous, as well as ozone. The number one dangerous trend in reef tanks is current-hungry equipment on inadequate house circuits in close proximity to saltwater. If people aren't harming themselves, why would you care what somebody you've never met does as part of their hobby?