All BS. I've done the ice water I've done the darkness, neither do anything positive for yield or potency.
As for the ice water IDK, sounds silly.
As for darkness here is what Serapis on here said once "Here is the deal, as I read it. The plant needs sugars and starches when it photosynthesizes. At night, those compounds travel back down to the roots where they are stored until the next day. If you allow all of the starches and sugars to drain back down to roots, and then chop the plant before it sees light again, technically, you are drastically reducing the amount of sugars and starches that need to be broken down in the curing process. This results in a smoother smoke, much faster than a traditional day time harvest."
Here is another piece I found on darkness-"
I decided to harvest three identical plants, all grown in the same room, at different times throughout the room’s light cycle. The first plant was harvested right before the light cycle occurred. The second was harvested right after the light cycle finished. The final plant was moved to a completely dark, temperature and humidity controlled room where it sat for 48 hours and was then harvested.
There was no noticeable difference in cannabinoid potency. We tested three samples from each plant and averaged the results of each plant to compare to one another. The results were virtually identical. There was no difference in potency in relation to the time at which the plants were harvested. Since machines are not always accurate, we also provided a few patients with blind samples to see if they noticed any differences in the samples. No differences were noted.
It is true that resin production on a medical marijuana plant peaks during the dark cycle. Because of this fact, there has been a myth perpetuated that cannabis harvested right before the light cycle begins — or cannabis given 24-72 hours of dark before harvesting — will produce a higher potency medicine than medical cannabis harvested during the light cycle. The problem with this theory is that a typical medical marijuana plant has a blooming period of about 50-60 days. When the overall time of the blooming cycle is taken into consideration, an additional day or two is pretty insignificant. The essential oils and resins are not produced overnight but instead are steadily built up over the entire blooming process. The number of cannabinoids degraded in one light cycle is completely negligible when comparing potency of the final product."
But experience is the best advice and from mine both these are myths, and unfortunately even some seasoned growers like subcool believe in this nonsense. Try it, compare, make your own opinion.