High Phosphates, but low nitrates

[max_reef937]

So I have a 32 Gal Fluval Flex that has been running for about 9 months now. Recently, I had a couple Zoas and a GSP that have been closed up for a few days so I decided to test my water. The results were:

Ammonia: 0.0
Nitrite: 0.0
Nitrate 0.0 (checked twice w Hanna checker)
Phosphate:0.37
Alk: 10.4
Calcium: 534

Could it be the high calcium, or lack of nitrates? Also, what’s the best way to reduce my phosphates?

I’ll note the rest of my corals all seem to be doing well. I have a couple scolys, candy canes, Duncan’s, Xenia, Kenya tree, other zoas, and a leather coral.

Thanks in advance for any advice or thoughts.

 

[Timfish]

What's your magnesium? Corals will periodcly close up and all corals may shed their mucus coating occasionally. If most of your corals look ok I wouldn't worry about a few being closed for a few days. I would do small weekly water changes though. Are you dosing alkalinity and calcium? If not your moderately high alkalinity and high calcium suggest your corals are not growing. FWIW PO4 at .37 isn't terribly high, upwelling exposes corals levels up to .2 mg/l and this paper found increased growth in an acro at .5 mg/l so I would lower it but I wouldn't consider it the source of your corals closing up. I wouldn't consider your nitrates an issue either, corals have mutualistic diazotrophs that will convert N2 into nitrates and actually preffer amino acids, urea ans ammonia over nitrates.

 

[max_reef937]

What's your magnesium? Corals will periodcly close up and all corals may shed their mucus coating occasionally. If most of your corals look ok I wouldn't worry about a few being closed for a few days. I would do small weekly water changes though. Are you dosing alkalinity and calcium? If not your moderately high alkalinity and high calcium suggest your corals are not growing. FWIW PO4 at .37 isn't terribly high, upwelling exposes corals levels up to .2 mg/l and this paper found increased growth in an acro at .5 mg/l so I would lower it but I wouldn't consider it the source of your corals closing up. I wouldn't consider your nitrates an issue either, corals have mutualistic diazotrophs that will convert N2 into nitrates and actually preffer amino acids, urea ans ammonia over nitrates.

I Didn’t test MG. I’ve been doing weekly water changes of about 20%. I have been dosing calcium and alk. What’s the best way to reduce Phos outside of water changes?

 

[Bucs20fan]

You need some nitrates for sure. Corals require those for sustenance. Them closing is not due to your phosphates, Ive had phosphate over 1.0 in a bad time, and soft corals were not affected. Calcium isnt high enough to harm anything, I would be looking at either your lighting where those corals are located, what is your salinity?

 

[max_reef937]

You need some nitrates for sure. Corals require those for sustenance. Them closing is not due to your phosphates, Ive had phosphate over 1.0 in a bad time, and soft corals were not affected. Calcium isnt high enough to harm anything, I would be looking at either your lighting where those corals are located, what is your salinity?

Middle 3rd of the tank. I have some zoas right next to the ones that are closed up that are doing just fine so it could just be those ones being weird. Salinity is 1.025 and temp is 76.4

 

[Timfish]

I Didn’t test MG. I’ve been doing weekly water changes of about 20%. I have been dosing calcium and alk. What’s the best way to reduce Phos outside of water changes?

GFO will drop your phosphates, just be sure not to go below the .03 mg/l threshold to prevent PO4 deficiency in your corals. I like weekly water myself but reduce the size of your water changes if you want 20% - 30% monthly works fine. Ph, alkalinity, calcium and magnesium can move independantly but effect do each other so I would be testing magnesium also. If you're dosing alkalinity and calcium you can reduce amounts with both of those that high.

FWIW I wouldn't be making any major changes if most of your corals seem to be fine. All I would be doing from you describe are small tweeks to what your doing and waiting to see how everything reacts before making another tweek.

 

[max_reef937]

Thanks! And yeah, I’m not huge on chasing numbers. I won’t do anything drastic since everything is doing well. I do want to get an anemone so just want to get the Phos. Down and find the routine to keep that stable before I do that and potentially create more issues for myself.