Phosphate: How low is too low?

[bureau13]

My phosphates have been hovering around 0.05 and 0.04, according to my Hanna ULR checker. However, this week I got a 0.03. Not much of a difference, and could just be I got it at low point of some mild fluctuations, but it got me thinking: How low is too low? At what point is it prudent to dose?

 

[bradreef]

0 is too low. If you get close I would recommend dosing or feeding heavier to increase.

 

[Reeferbadness]

I've had mine go to 0.01 and 0.02 and was ok in both of my 200g mixed reef tanks, i've also had mine go up to .15 or so and still all was ok. I even had a spike up to .57 when traveling and still all was ok (but growth slowed considerably as measured by the uptake of Alk ). I think that people obsessing over phosphates is a bit overblown. Keeping things as steady as possible is (of course) key. If you want to raise them slowly, just feed your fish a little more or more often.

 

[CHSUB]

I have healthy corals, growing mangroves, and algae on the glass and occasionally get this reading…but also readable sometimes.

 

[exnisstech]

I'm fine with anything but zero. I'll dose if I see zero because I've read nutrients bottoming out can cause a dino outbreak. I've never had dinos so I'm continuing that method. I'm not as brave as @CHSUB . While they have a stunning tank I just can't bring myself to run at 0.

 

[CHSUB]

I'm fine with anything but zero. I'll dose if I see zero because I've read nutrients bottoming out can cause a dino outbreak. I've never had dinos so I'm continuing that method. I'm not as brave as @CHSUB . While they have a stunning tank I just can't bring myself to run at 0.

I agree and prefer a readable number, when 0.00 I get heavy handed with food…

 

[BetterJake]

My phosphates have been hovering around 0.05 and 0.04, according to my Hanna ULR checker. However, this week I got a 0.03. Not much of a difference, and could just be I got it at low point of some mild fluctuations, but it got me thinking: How low is too low? At what point is it prudent to dose?

I’d start feeding a bit heavier. The last thing you want is phosphate bottoming out, which raises the risk of dinos. Corals also benefit from some phosphate. You could increase fish feedings, dose phosphate product, or add a pinch of Reef Roids (or a similar coral food) once or twice a week.

 

[Salty_Northerner]

Whenever I get 0.00 on my phosphorus ulr I always get a dino outbreak. Not fun and is a real pita for months afterwards. My tank was always on the consumption side of sucking up po4 for almost 2 years. Suddenly after 2 years the tank is able to hold .04 po4 and things are going so much more smoothly thank God!

 

[exnisstech]

Whenever I get 0.00 on my phosphorus ulr I always get a dino outbreak. Not fun and is a real pita for months afterwards. My tank was always on the consumption side of sucking up po4 for almost 2 years. Suddenly after 2 years the tank is able to hold .04 po4 and things are going so much more smoothly thank God!

My SPS tank was similar and required dosing N and P off and on for the first couple of years. I was able to stop dosing PO4 first so I switched to ammonia bicarb for NO3 and eventually was able to stop that also. Levels are low but as long as they're present I figure it should be enough for coral.

 

[DaveC]

My wild, unscientific guess is that depending on your tank, if you bottom out N & P you run a high chance of wiping out a good portion of the beneficial bacteria and the dreaded dianos take over.

 

[gbroadbridge]

Remember that the potential error on the Hanna ULR is +/- 0.03.
So if you're reading 0.03 It is possible that the level is really 0.00

So I alway try to maintain 0.05 or above.

 

[CHSUB]

My wild, unscientific guess is that depending on your tank, if you bottom out N & P you run a high chance of wiping out a good portion of the beneficial bacteria and the dreaded dianos take over.

Bacteria are more resilient and capable of survival than any other known organism, even viruses need a host.

https://hms.harvard.edu/news/how-dormant-bacteria-return-life
https://news.mit.edu/2013/how-quickly-can-a-bacterium-grow-0827

 

[DaveC]

Bacteria are more resilient and capable of survival than any other known organism, even viruses need a host.

https://hms.harvard.edu/news/how-dormant-bacteria-return-life
https://news.mit.edu/2013/how-quickly-can-a-bacterium-grow-0827

Thank you for sharing!

 

[Randy Holmes-Farley Verified Community Expert]

I give my recommendations and rationale for them here:
https://www.reef2reef.com/ams/randy’s-thoughts-on-nutrient-target-ranges.1087/
. What targets seem reasonable? Of course, that depends on all the other factors at play, such as types of corals, availability of ammonia, particulate foods, etc. However, for a mature mixed reef, this would be how I personally would run it:

• Let nitrate float between 5 ppm and 50 ppm. I’d use gentle export in this range, such as growing macroalgae.
• Above 50 ppm, I’d begin to focus more on reducing it, by organic carbon dosing, turf or macroalgae, etc.
• Below 5 ppm, I’d begin to dose ammonia or feed more. The target level might drop lower if dosing ammonia, just like the heavy in/heavy out scenario where nitrate may not be as needed.
• Let phosphate float between about 0.06 ppm and 0.3 ppm. This range is higher than I’ve recommended in the past. I’d use gentle export in this range, such as growing macroalgae.
• Above about 0.3 ppm, I’d begin to focus more on reducing it, by turf or macroalgae, or a binder such as GFO or lanthanum (has its own risks to tangs). If a binder: GO SLOW. Turf and macroalgae will typically be slow enough.
• Below 0.06 ppm, I’d begin to dose sodium phosphate or feed more to get the level up.

 

[BryanM]

I really like mine to be .1-.3.

This is just an odd area where there are so many viewpoints. All of my ICP tests want .02 or .03, which I think is way too close to zero for MY personal comfort zone.

 

[MichaelM]

I never got dinos with undetectable phosphates but when they got really low many SPS would RTN (frags will be completely gone over night). Having some buffer against zero is good, exact numbers don‘t seem to matter.

 

[CHSUB]

I never got dinos with undetectable phosphates but when they got really low many SPS would RTN (frags will be completely gone over night). Having some buffer against zero is good, exact numbers don‘t seem to matter.

This is true; life doesn’t bloom, overrun when nutrients are low…they wither or barely survive!

 

[Randy Holmes-Farley Verified Community Expert]

This is true; life doesn’t bloom, overrun when nutrients are low…they wither or barely survive!

While that may be true, it really doesn't bear on the point that something else whithering may open up the tank for dinos.

Fire doesn't make wildflowers do anything but die, but if a fire beats back competitors, such as oak trees in a forest, the wildflowers can then spread readily.

 

[MichaelM]

The intention of my post was simply to raise the topic of coral health. The other posts seem to focus only on the dino issue, but even when dinos aren’t present, corals can still be lost when phosphate is really limited.

 

[CHSUB]

While that may be true, it really doesn't bear on the point that something else whithering may open up the tank for dinos.

Fire doesn't make wildflowers do anything but die, but if a fire beats back competitors, such as oak trees in a forest, the wildflowers can then spread readily.

I agree with your wildfire example in nature and in “real life”, however disagree in glass boxes. I use the example of slow growing mangroves in estuaries. Near the ocean, mangrove dominate because they have an ability to filter saltwater and their slow growth is not a limiting factor. Upriver in freshwater, with their slow growth, they disappear because faster growing vegetation occupy all the real estate.

In glass boxes, I don’t believe dinoflagellates are outcompeting bacteria and other algae. They are right there with everything else consuming nutrients. Difference is many believe that dinoflagellates are the “boogeyman”; instead of cleaning, maintenance, and manual removal they look for “easy” fixes to a believed super enemy.