High PO4 (0.27 ppm) / Low NO3 (2.5 ppm)... Best Method(s) to Resolve?

How to best resolve a nutrient imbalance with a high PO4 (0.27 ppm) and low NO3 (2.5 ppm)?

  • Increase NO3 to 5-10 ppm with sodium nitrate in the assumption PO4 removal is NO3 limited.

    Votes: 4 40.0%
  • Reduce PO4 with GFO and live with an NO3 of 2.5 ppm.

    Votes: 4 40.0%
  • Increase NO3 to 5-10 ppm with sodium nitrate and reduce PO4 with GFO.

    Votes: 2 20.0%
  • Increase NO3 to 5-10 ppm with sodium nitrate and reduce PO4 with a refugium.

    Votes: 0 0.0%

  • Total voters
    10

mstgkillr

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I'm looking to resolve my current nutrient imbalance with a high PO4 (0.27 ppm) and low NO3 (2.5 ppm)?

I have a mixed reef/SPS dominant, Red Sea 900 3XL (240 gallons total), no refugium and a Bubble King Double Cone 180. No rollermat (waiting to reinstall) or filter socks. High bioload (Naso, Gem, Sailfin, Blue, Purple and Yellow tangs; clownfish and at least 7 other smaller fish). I feed 2-4 sheets of nori and 3 cubes of Reef Frenzy daily and my fish are fat.
 

alxrosco

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I use BRS high capacity GFO. It will only decrease your Phosphates, not the nitrates.
 
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mstgkillr

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I decided to go with option 1 and increase my nitrate between 5-10 ppm, in the hopes that my tank is nitrate limited. Hopefully it won’t fuel an algae outbreak.

Yesterday, the nitrate was 2.5 ppm and I dosed another 2.5 ppm of sodium nitrate. Today, the nitrate is still 2.5 ppm, but the PO4 dropped from 0.27 to 0.18 ppm, so I added another 2.5 ppm of sodium nitrate and will test again tomorrow.
 
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mstgkillr

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Today, the nitrate is 5.0 ppm, but the PO4 only dropped to 0.16 ppm, so probably not nitrate limited. I’m thinking adding GFO or a refugium.
 

Gtinnel

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I'm trying to decide the same thing but my phosphate have been staying around .18 recently and my nitrate stays around 2 with me occasionally dosing manually when it gets down to about 1. If there are nitrates at all in the system can the system be nitrate limited?
 

Mywifeisgunnakillme

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Yeah, I would do gfo and feed more. But I idk if that’s what you should actually do.
I don't disagree. I just try to feed enough so that all the fish and inverts get fed. If crabs and the like start starving, or fish don't look a little plump, i boost the feeding and do what i have to control nutrients within reason (less than 40ppm nitrate and less than 0.25 ppm phosphate is fine by me if no nuisance algae issues). On some tanks i've had i don't have to test because the numbers never really change, often nitrates being 0 despite heavy feeding (IMO). Other tanks nitrates seem to rise, and i am not sure why. If nitrates go over 50ppm i figure i should do something and if phosphates over 0.3ppm i think the same. I do notice certain acros change color based on nutrient levels, but they always look nice and grow well!

I wouldn't worry about the ration between nitrate and phosphate unless an issue like dinos pops up.
 

X-37B

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How big are the cubes? how much GFO do you run? Just curious, no criticism here...
Cubes are from the boxed roll so they are bigger than the standard box cubes.
2 mysis 2 brine twice a day.
With some larrys and green cubes, plankton, krill cubes alternated with the brine.

I typically do not like gfo as its a mess to use but had a bunch I wanted to get used up.
I was running 2 cups in a nylon bag.

I just stopped running it and am now back on phosgaurd. I run 500 ml with 1 cup of carbon in a nylon sock.

My old reactor was a small aquamax.
I just replaced it yesterday with a lifegaurd medium top flow reactor.
20211002_111750.jpg
 
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