Could Carbon = STN

The magnet is a prime suspect,imo.. It can each nasty free metals. The carbon and gfo may help remove some of them. Fortunately, overtime most free metals will bind to organics and be much less toxic. Poly filter may be useful. Sometimes when a coral is stressed red bugs and other pests get a leg up.

On that note, may want to check heaters and pumps for rust / leaks. Sadly it happens way too often. If you run filter socks you may see concentrated streaks of rust as an indicator of any free metals.
 
I stopped using GFO a few years ago due to STN issues and I discontinued continuous carbon 2 months ago. Even when I changed out a small amount of carbon, I could occasionaly still see a small flare up of STN. Now I use my diatom filter about every other week or so charged with powdered norit carbon. This cleans the water better than any other carbon I have used (including ROX) and there is never any STN afterward.
I have a theory about why this is and what happens when you change out any media, especially in large amounts. I always noticed a large bacterial "mess" present when I changed out my old media and it made me think of the mulm that grows on Zeo rocks. Do you know what happens when you start Zeo and put in too many rocks too fast? STN and lots of it. It's not that the rocks or media are removing nutrients too fast. I suspect it's the sudden growth of huge bacterial populations that have found a new substrate to grow on. The more surface area there is , the more growth you get. Especially if you are carbon dosing in any form like Zeo or biopellets. This would explain why using carbon in the diatom filter for just a day does not produce STN but carbon (or any other media) left continuously does.
Just a theory of course. Facts are few and hard to find with the problems of reefkeeping:spin1:
 
The new surface notion might be an issue for better or worse but when you remove carbon to change it I would think at least initially more bacteria are being exported with it than are colonizing the new stuff. In any case new gac will alter the organics and whatever they hold to some extent and I prefer smaller changes at one time. I have not noticed stn after changes.
 
what amino acids are you guys dosing?

I use Elos amino acids. They last a LONG time. I dose 5 drops a day on my 75g sps reef. I had too low of nitrates and since dosing I have noticed an improvement in color for sure, and now I can keep nitrates at about .5ppm.
 
Latest update...

I have completely removed carbon from the system and treated for red bugs. Initially I also removed GFO, but after monitoring my PO4 for two weeks I found that the levels were creeping toward the higher side of my comfort level of .05 to .06ppm. I changed the GFO last week and decided to continue to run it based on the fact that it really does help keep the PO4 around .03 - .04 which seems a healthy level for everything.

I treated for red bugs yet again... this will be my second full round of treatments this year. I think that the true solution to my issue is the red bug treatment. Seven days post treatment the ALK went from a stable 8.4 DKH down to 7 because of the recent growth and re-encrustation of the corals that had been retreating and STNing. I am really crossing my fingers that a lot of the frags that are almost totally lost will recover. This whole process has been incredibly frustrating because in the past I could actually see red bugs and therefore I felt more comfortable treating the tank. This time around I found what I thought were a few but the evidence wasn't convincing until post red bug treatment and obvious coral growth. There certainly could be other factors in play too as I did in fact find a leaky magnet and I also adopted a full regimen of Instant Ocean saltwater changes... I was trying to switch to Red Sea coral pro but I gave up and decided that I should return to what was previously working for me(a 40/60 mix of IO and Reef Crystals), not to mention less expensive.

Thanks to everyone for their continued input, I can't say enough about how invaluable this resource of Reefcentral has been to the success of my venture in this hobby!
 
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