I think, unfortunately, that some of the OP's disappointment just stems from impatience. I have one 75g tank that's been running for almost 25 years. It is nothing, and I mean nothing, like it was in the first couple of years. Our tanks just take time to stabilize, sometimes much more time than we realize or are able to accept. It's been said countless times that nothing good happens quickly in a reef tank. It's rarely as well pointed out that for a reef aquarium, a year is just a flash in time.
I firmly believe, although I have no real proof and only anecdotal evidence for this, that constantly messing with the chemistry and biology of our tanks is among the worst things we can do. Conversely, I think one of the best things we can do is to make a plan and stick to it for the long haul. Run GFO or carbon if you choose to. Use bioballs if you think it's good to do so. Run a Ca reactor if you want to. Do regular water changes with the same saltwater mix. Feed the same amount at about the same time(s) every day. Choose appropriate lighting and maintain your lighting schedule. But don't waffle back and forth between using these things and not using them, or between saltwater mixes, or lighting programs. Stability, IMO, is key.
And just for some real evidence, I checked my PO4 in that 75g system last week: 0.83ppm. I can hear hearts fluttering right now. Yes, that number is correct and verified. It probably spiked to over 1ppm after feeding every day. That tank has not the slightest shred of nuisance algae, and hasn't for many years. Some cyanobacteria does accumulate on the sand bed at the end of the day, but it doesn't bother anything. The tank has SPS, LPS, zoanthids, discosoma, goniopora, all healthy, growing, and thriving, and a lot of that stuff has been in the tank for its whole life. I've had the same fish in the tank for a really long time, ranging from a 30+ year old yellowtail damsel and a 20 year old rabbitfish to a 4 year old falco hawkfish. I've had the same pair of skunk cleaner shrimp for more than 5 years, and the same banded trochus and nassarius snails for going on 10 years.
All of which is just to point out that good things take time, and stability is key. Patience is not only a virtue, it is a necessity for this hobby. Those who cannot find patience are doomed to fail or quit.
I'll also point out that for the life of me, I cannot keep a cynarina in this tank long term. I love those corals, but for some reason I cannot maintain one in that tank, so I gave up trying. Sometimes we just have to accept things like that.
