Let's talk phosphate levels

[Randy Holmes-Farley Verified Community Expert]

There are not many seemingly simple reef chemistry issues that are more vexing than phosphate.

Years ago we assumed that matching the ocean was desirable, but those levels seemed too low in practice (likely due to lack of particulate sources of P for corals in reef tanks). Then we read papers that showed reduced calcification of corals by elevated phosphate (it also does inhibit abiotic precipitation), and we picked low target levels. But is that really true in reef tanks? It seems maybe not, or at least not enough to be problematic.

So this poll is intended to help answer a very focused question about what phosphate levels are desirable. I'm not asking what levels you run, or what levels you read are best, but specifically if you have ever had high phosphate, and then lowered it, while doing not much else, and observed a positive and lasting effect on corals.

For purposes of this question, let's ignore any and all effects relating to pest algae, cyano, fish, etc.

Just coral effects for both hard and soft corals of all types. Effects can be color, growth rates, expansion/inflation, or a general perception of health. Please give some explanation in the follow up posts if you saw some type of positive effect.

 

[Randy Holmes-Farley Verified Community Expert]

FWIW, negative responses by corals may get confounded with the rate of drop, so let's not focus on that in this poll either.

Thanks in advance.

 

[Dr. Reef Verified Sponsor]

My phos levels are 0.03-0.05 range and everything seems to be just fine. Trident, trident NP and multiple dos and ddr,
Amino acids being dosed and Lanthanum for controlling phos, auto water change for exporting nitrates.

 

[Pntbll687]

So I've had phosphate above 1ppm, and .5ppm for extended periods. I didn't notice any adverse effects, didn't have algae issues, and corals grew (could it have been faster, I don't know.).

I lowered phosphate to around .1 both times, but didn't observe any difference in growth rates or coral health/color that I could attribute directly to the lowering of the phosphates.

 

[A_Blind_Reefer]

For the most part I’ve typically had negative effects from lowering phosphate (I’ll clarify that, lowering using gfo. I’ve lowered it by adjusting lighting on algae with no ill effects). I’m assuming dropping too quickly, or stripping something else in the process. In the past I noticed pale, some even lost most all coloration and would be completely white, from running phosphate at the once touted 0.03 level. Dropping phosphate has typically ended with a piece or two starting to stn shortly after, or paleness. I can’t tell now but in the past everything seemed much better as a whole at any level from 0.07-0.4 (I haven’t gone over that on my current tank). I’m not saying everything suffered at 0.03 or from lowering phosphate, but there was always at least one (typically several) coral(s) that did. I have a mixed reef and truly don’t care what the level is as long as it falls somewhere between 0.07 and 0.4. If it’s outside of that, I’ll adjust. That said, don’t listen to anything I say as I currently have stn spreading around, ha.

 

[stalkem]

My phosphates have been greater than 0.4 pretty steady for a while. I've been trying to use PhosphateRX to lower them, but I keep getting fluctuation. Most recently (since I got my Hanna Checker), they were as high as 0.71ppm and I got it down to 0.23ppm. I'm trying to pinpoint why they keep creeping back up. I suspect it's my overfeeding to keep my dragonet fat and happy, but I also recently started using Benereef, so between that and the Reef frenzy in the mix I make for the dragonet. Everything else has been stable and happy, but I can't figure this Phosphate situation out.

 

[ChrisfromBrick]

My phosphates were hanging around in the .12-.15 range for awhile and lately have been going as high as 0.22. I dont mind any of those numbers. The only issues are some hair algae but there are much worse things to have present in a tank.

 

[GARRIGA]

Should there be a Richard Ross 2 ppm option :thinking-face:

 

[Cheezle]

I used Rowaphos to drop my Phosphate from 2.4 down to like .4 and everything seemed to turn around after that. It also seemed like my other parameters (ALK, pH, Ca, Mg, AMMO, Nitrite, Nitrate) balanced themselves out once I got my Phosphate levels down. Its been a night and day difference for my tank and the only thing I changed was instead of adding a bag of Chemipure I added a bag of Rowaphos instead.

 

[JayM]

I normally don't test PO4, but a few months back I noticed most of my LPS looked unhappy. It turned out that PO4 had risen to .5. I got it down into the mid to high .01X range and corals are visibly better off.

What I don't know is whether or not phosphate spiked to .5 quickly, or if it was a slow rise that caused the problem. Either way, lowering PO4 and keeping it in the .07ish range made them appear healthier overall.

 

[Randy Holmes-Farley Verified Community Expert]

I used Rowaphos to drop my Phosphate from 2.4 down to like .4 and everything seemed to turn around after that.

What appeared to change?

 

[ccole]

In my old tank, I noticed polyp extension and coral health looked the best between .1-.2. Anything above .2 and things started to look a little less healthy and they’d improve again once I added GFO.

Currently I’m having trouble keeping phosphate above .03. Dosing phosphates daily seems to keep them happy.

 

[sixty_reefer]

In one of my older thank I did see the best growth of coral under high phosphate 1.9 mg/l plus.
I’ve never tried to reduce it if I remember correctly.

 

[Randy Holmes-Farley Verified Community Expert]

In one of my older thank I did see the best growth of coral under high phosphate 1.9 mg/l plus.
I’ve never tried to reduce it if I remember correctly.

Hard corals or soft corals?

 

[VintageReefer]

My phosphate was .02-.05 for over a year and then I increased to .5 and now I maintain .4-.5.

I don’t really feel there’s any change in the corals, although since the increase I’ve lost 3 acantho’s and now I’m losing my 4th. I am honestly not sure if it’s related, it’s the only coral affected. Does fine for a few months then declines over the next few months.

Other than acanthophyllia, all other corals are looking great including other donut coral like Cynarina and scolymia and sensitive species like acropora and goniopora

 

[TinCanHero]

I struggled for a few years when I started out getting things, especially SPS to grow well. id find as time went on the problem got worse. ICP tests showed params where all good so I was at a bit of a loss. tank was clean with no algae etc but nutrient levels where high. it wasn't until I reduced my nutrient levels down and got phosphates under control did I get any results with SPS and my LPS rocked on also. it was a real turning point understanding keeping free phosphates low and stable is as important as KH for good growth.

I think it was Lou from TM that made the lightbulb go off for me when he was talking about carbon dosing and how phosphate is usable

 

[14 foot reef]

I typically ran my pO4 at .15-.2 without any adverse effects or negative results in coral color or growth.
I recently spent about 6-8 weeks lowering my pO4 with Phos RX at half dose to the .04-.06 area and I will say that I have Lost a a big Monti and bleached out a couple acros, I followed the half dose on the Phos RX but since I have never lost a large monti or bleached out acros, I would directly relate this to the Phos RX. I can't scientifically prove it, but the lowering of the pO4 through Phos RX is the only thing I have changed during this lowering of pO4.

 

[sixty_reefer]

Hard corals or soft corals?

SPS and LPS at one point I did observe a decrease in alkalinity and calcium consumption but corals never stopped growing, it was a 2 years experiment with live phytoplankton hence the high phosphate.

https://www.reef2reef.com/threads/continuous-phytoplankton-rotifers-reactor-24h-food-supply.526123/

 

[Cheezle]

What appeared to change?

Just seemed like everything in general improved. Corals that I had owned for years like my Duncans had heads die off while becoming short and stubby. They recovered very quickly, became fuller and more dense, sprouting more heads. My anemones went from splitting a lot, being short, stubby and kind of "brown" to becoming massive and full of color again. My rock flowers did something similar but oddly enough some shrank while others got bigger, both losing color or gaining some. My mushrooms stopped splitting as well and just seem to be happier in general.

I've seen people say these aren't very accurate but its what my LFS uses and were taken 4 weeks apart, I noticed things start to get better during that initial 4 weeks as well. I do 5 gallon water changes a week but I didn't see any real improvement until I started using Rowaphos.

Could just be my tank maturing or a coincidence of when my tank started getting better vs when I started using Rowaphos but I'm a firm believer that getting my Phosphate levels down helped establish balance in my tank

 

[vandy]

I suddenly had a spike from .1 to .7 and lost a few of my higher end acros. I'm jealous some people's corals are growing at above 1ppm phosphate levels.