Optimal Phosphate Levels, Then, and Now

[ReefGeezer]

Hey everybody. I'm curious. When did the consensus regarding optimal phosphate levels change and why? I've been around a while and remember when 0 was (certainly wrongly) optimal. Then .03 ppm became the target. Now it seems that any level below maybe .3 ppm is just fine. What happened to the study that showed that phosphates above a few hundredths of a ppm inhibited SPS growth?

My mixed reef seems fine at .1 ppm. Would it be any better at .03? Would it be the same at .3?

 

[Kooma]

I’ve had between near 0 and 0.6. I noticed a lot more angry coral at 0 than at .6. The ideal comes from seawater. The aquarium number comes from adverse effects and ease of maintenance balance.

 

[Randy Holmes-Farley Verified Community Expert]

It may be true at the same time that higher phosphate slows SPS growth, and that it also can lead to very nice tanks, Many reef tanks don't really aspire to have faster growth.

Tracking the Richard Ross experience, which is a great example of much higher than usually recommended phosphate, he has not noticed much change (good or bad) as he has slowly lowered phosphate from 1 ppm to lower values.

Hopefully I characterized his long road of phosphate accurately enough...
@Thales

 

[CHSUB]

0 was never the goal, at least in my circle. Undetectable, yes but my first po4 test kit started at .2 ppm iirc. I still prefer around .02 ppm on my Hanna and just ordered some GFO to get lower from ~.1 ppm. I would guess most experienced reefers are around my target. Some people are obviously higher but that might be people who participate online or get in discussions?

 

[areefer01]

Maybe asking the wrong question. I would have asked 'When did hobbyist actually care about phosphates?'

Possible answers:
When hobby level test kits became consistent or affordable
Market driven
Social media and influencers
Fads (negative aquascape, ultra low, Zeovit like methods)

Being a hobbyist who also has high nutrient levels, including phosphates peaking at 1.9 ppm, one thing I learned is not to panic and know what works in my system. In short if something does not do well I do not rush to replace it with the same thing. I do my best to understand what I did, what I can change, and if it will help. I do not replace it unless I know what I did or didn't do.

Works for me /shrug

 

[Thales]

Hey everybody. I'm curious. When did the consensus regarding optimal phosphate levels change and why? I've been around a while and remember when 0 was (certainly wrongly) optimal. Then .03 ppm became the target. Now it seems that any level below maybe .3 ppm is just fine. What happened to the study that showed that phosphates above a few hundredths of a ppm inhibited SPS growth?

My mixed reef seems fine at .1 ppm. Would it be any better at .03? Would it be the same at .3?

That study and its utility to the hobby are a great story about why we have to be careful of applying studies to our tanks. The question about that study that I think is the most important is not if it showed inhibited growth or calcification, but how much inhibition was recorded. IIRC, when I did the calculations, it was less than 8%, and I don't think the juice is worth the squeeze over 8%.

Besids that, the million monkeys effect comes into play. As people do stuff in reef tanks, we get useful anecdote. The number of awesome tanks that have success at 'higher' levels of phosphate and nitrate become unignorable over time.

But we have been having this discussion since at least 2010. :D

 

[Thales]

It may be true at the same time that higher phosphate slows SPS growth, and that it also can lead to very nice tanks, Many reef tanks don't really aspire to have faster growth.

Tracking the Richard Ross experience, which is a great example of much higher than usually recommended phosphate, he has not noticed much change (good or bad) as he has slowly lowered phosphate from 1 ppm to lower values.

Hopefully I characterized his long road of phosphate accurately enough...
@Thales

That sounds right!

 

[ReefGeezer]

0 was never the goal, at least in my circle. Undetectable, yes but my first po4 test kit started at .2 ppm.

I suppose I meant undetectable rather than 0. That was a long time ago. Seems like the ULNS methodology was still in vogue when I bought my Hanna ULR Checker. It is accurate to a few ppb if I remember correctly. I still use the one I bought back in the day.

It may be true at the same time that higher phosphate slows SPS growth, and that it also can lead to very nice tanks, Many reef tanks don't really aspire to have faster growth.

Tracking the Richard Ross experience, which is a great example of much higher than usually recommended phosphate, he has not noticed much change (good or bad) as he has slowly lowered phosphate from 1 ppm to lower values.

Thanks Randy. I hear you when you say many things can be true at the same time. I understand those truths depend on the corals present in the tank and the expectations of the hobbyist. I looked up Richard Ross and watched some of his videos and read some from the links.

So, let me restate my question. When managing a reef tank for SPS coral growth and color, is there a consensus phosphate level to target?

 

[winzig]

I run at .6 to .8 and both my tanks are doing fantastic.I just don't have sps

 

[CHSUB]

suppose I meant undetectable rather than 0. That was a long time ago. Seems like the ULNS methodology was still in vogue when I bought my Hanna ULR Checker. It is accurate to a few ppb if I remember correctly. I still use the one I bought back in the day.

I stare at my tank @ .13 ppm po4 and see one particular coral, Monti Setosa. A once thrilling pink is now more of a dark red. While it has become partially shaded do to a Bird Nest coral and now receives yellow spectrum light, I wonder if this coral’s color change is partially due to an increase of po4 in the last few months? This is why some hobbyists try to keep nutrients low and others will say for example, “that good enough”…

 

[MegabiteOG]

I was absent for 15 years before coming back and undetectable was what I strided for back then. I was surprised what is considered acceptable today. My tank has been sitting at .2 PO4 for a while now and I have a lot of sticks. They all seem to be happy at this level though in my mind I can't help to think that it's too high for SPS due to the years of experience from back then.

I took a bunch of picks of mostly sticks today and put them on my tank thread. You can see that these are happy corals. For now, I'm letting it ride as the tank is very stable at this level.