It has been slowly receding, what would you use to dip? Tank is about 3 months old but used all live media and lots of different bacteria added. Parameters have stayed consistent.
I think just over filtration at times, I have slowly taken out some bio media so it doesn't go too low.do you know why it dips like that sometimes?
In my opinion, that is your culprit right there!
Using nanospect bio bricks (2), some of their bio balls as well, chemi pure blue, UV, weaning off nopox to use algae scrubber, protein skimmer. Have some live rock and some dry rock that is probably sucking in phosphate.
if I were in your shoes, I would pull the bio bricks, bio balls, chemi pure and cease NOPOX without more hesitation.
the nitrates were up at around 30-40 so the reason for having nopox was to bring it down now it maintains a steady 10. Im a little hesitant on removing them all at once so maybe start slow?
You have a number of "unwanted" demands on the system's available dissolved phosphate.
You can even keep the biomedia live (wet) for a while as a fall back plan....it would start working immediately like it had never been removed. Wow thank you so much for the detailed response the picture really does put it into perspective. You have me convinced, the last thing I ask is what would you have your nitrates and phosphates running at?
You have a number of "unwanted" demands on the system's available dissolved phosphate.
Carbon dosing (nopox) mostly depends on increasing bacterial mass to reduce nutrients. That requires N and P....and if N is out of balance, that means you will tend to drive P to zero. Plus you're using GFO in the chemipure.
Arguably you might have elevated N in the first place due to the excess bio-media....many reef organisms will utilize ammonia, some may almost require it. But bio-media, by design and intention, serves only to proces NHx into NOx at the fastest rate possible. (Bacteria will use it up faster and to a lower level than anything else, given the conditions.) That's great for a fish tank filter, but not really geared to how a reef works.
As far as hesitating...of course that is up to you, but I will add some more thoughts:
IMO once you solve the mystery (IMO: ☑), then that's cause for action.
Unless the tank is nursing a latent hair algae outbreak....and/or you have an undisclosed knack for overfeeding....and as long as the proportion of live rock is "right" in your tank (ie not some "ultra minimal" setup), I don't think I'd hesitate pulling all of it at once.
That said, if you want to (for example) stop GFO and nopox today, pull 1/2 the biomedia tomorrow and 1/2 on thursday or something like that, then no biggie....but I wouldn't draw it out too much.
Feel free to run an ammo alert badge or otherwise scale up your testing during the transition if it will help you be confident about what's going on in the tank.
IMO there's only upside to doing this....risk is either nil or almost zero. (There is definitely more risk in doing nothing.)
Check out this journal article that really shows (in pictures) what your coral is going through with the low/dipping phosphates. Your coral is still in the early stages of the third scenario, "HN/LP":
