Phosphates through the roof with zero nitrates

[pandaparties]

520 gallon mixed reef and predator tank. I have been dealing with some gha the past few months and i felt like i had turned a corner these past couple weeks, have a lot less of it and a lot of my coral was looking awesome. The past week though i noticed my acros had all lost a lot of color and one of my chalices had some loss of tissue. All my euphillia still looks super happy as does most my lps in general my phosphates keep going through the roof. I haven't been running a refuge or my reactor, i don't dose carbon right now or use gfo.

Parameters:
1.025 salinity
77-78 temp
8.8 alk
1380 mag
500 calc
nitrates constistently 0
phosphates have been ranging from .4 to .6

Stocking:
about a dozen pin cushion/tuxedo urchins
Blonde Naso Tang (10 inches)
Vlamingi (7 inches)
Purple Tang (5 inches)
California Common Stingray (id guess like 7 inches in diameter)
Marbled Catshark (12 inches)
bird wrasse (5 inch)
Cherry Grouper (3 inch)

I am going to starting running GFO but really not sure whats going on here. Every time i try feeding more nitrates stay bottomed out and phosphates keep climbing. I have tried salifert and numbers are consistent. I also run a calcium reactor with reborn media.

 

[pandaparties]

I run 4 filter socks that i change bi-daily and i have a reef octopus 6000sss skimmer running, as well as an 80w UV

 

[youcallmenny1]

Generally when that happens it's because I'm underfeeding and the tank is starving. I use a fuge and my macroalgae needs nitrates to grow. When it grows it eats both nitrates and phosphates. Ergo, no nitrates = no phosphate export. Not sure if you have a fuge but I've been down this very destructive rabbithole and that was my solution. Feeding more seems insane in that position but it worked. I should add that I started running a phosphate reactor initially to combat the high PO4 (phosguard, not gfo) and that nuked most of my coral and shot my aluminum through the roof! Having removed my carbon/phosguard reactors and feeding until nitrates were up to 5-10ppm, things did a 180 and are growing away already. The phosphates were at 0.15 when I started all this and I have a hard time keeping them above 0.05 now. It's very easy to overfilter our tanks with modern equipment and you are being VERY diligent about your maintenance.

 

[BroccoliFarmer]

I had the same issue. I am assuming you are running macro algae (cheato)? Macro algaes update nitrate faster than phosphates. As such, the more you feed, the higher your phosphates will actually go because your macro algae is sucking out the nitrate too fast. The solution...dose nitrates. By adding additional nitrates, your cheato can keep up with the phosphates.

 

[pandaparties]

I'm actually not running any chaeto though I suspect my GHA is acting like chaeto instead based on these responses. Also I feed two frozen cubes, a handful of silversides and a sheet of nori daily which I already felt was excessive lol

 

[youcallmenny1]

Yikes. I was afraid you would say you had no fuge. Your situation is beyond my experience then and I'll shut up and follow the thread to hopefully learn something.

 

[Randy Holmes-Farley Verified Community Expert]

I can think of a few possible reasons for excess phosphate relative to nitrate in this situation:

1. The phosphate is coming from rocks or sand that previously had been exposed to substantial phosphate.
2. Phosphate is coming from foods that have phosphate applied as a preservative, such as fresh or frozen seafoods.
3. There is substantial denitrification happening the the sand or rock or other media, which reduces nitrate and not phosphate.

 

[sixty_reefer]

Hi I would just add some no3 to help rebalance the system. Adding no3 should help you lowering the phosphate and Keef a decent reading of no3 to avoid a bloom of dinoflagellates. ATI nutrition could be a easy of the shelf method to help you.