My reef tank, even though its fullblown is fairly new. Also my Po4 is not .5, it hovers around .1 - .4, but close to .5, but never saw that high. But that's why I put in all caps ADAPTABILITY. acros tend to adapt well over time. And I have nothing But High end acros. Problem with having low nutrients for long periods of time in a enclosed system, and to maintain and have them adapt to low nutrients is harder to maintain in the long run. Also to succumb to more problems down the road. With all these other products that these companies want you to use. Why do you think alot of newbies have problems with dinos, and other nuisances. Because they believe low nutrients is the key to success and not knowing dinodinoflagellatess are so very present in every system and very opportunistic, and once you start using AB+, aminos, and other broadcast foods. BOOM, ....outbreak.While this is great success, newcomers to hobby will be thrown off by thinking 0.5 ppm PO4 will work. The more mature and the more nutrient cycling, the higher the system tolerates phosphates. Many new tank would not fair well like that.
You want resilient corals, and have them ADAPT in a stable system long term. That's why I keep my nutrients (Po4) in that range of .1 - .4