How important is PO4 stability really?

[george9]

Hi all,
Over the last few weeks I am once again having trouble keeping po4 steady. Between October - February I was able to keep PO4 steady between .04-.08 easily. Since late February, my po4 has once again been getting too low, sometimes testing at .01 or .02. It’s been about 2 weeks since I’ve tested that low, but I am still seeing fluctuations. I attribute the downward trend to too many water changes and less feeding which slowly allowed the concentration to drop. I am trying to balance it between .08-.12 now (slightly higher than before) with increased feeding and dosing but it has been a struggle to keep it consistent. I feed Reef Roids last night and this morning it spiked to .14ppm which is the highest it’s ever been in this tank.

This is all while the corals look really good and are growing. I keep telling myself to stop chasing numbers and pay attention to coral health, but I can’t help but think a po4 roller coaster has to be bad for growth long term.

TLDR - Is varying phosphate concentration a problem day to day as long as it’s within an acceptable range? Say I am at .08 one night, feed reef roids and spike to .15 the next day - that’s almost double what it was the day before. Will this cause issues for coral health? The last 10 days I’ve been as low as .05 and as high as .14 which in my head is too large of a range, despite the corals looking good.

I know that letting PO4 drift continually towards 0 will cause issues because that would be a situation where they don’t have enough to grow. but how about fluctuations when phosphate is within a healthy range?

Any experience is appreciated

Thanks!

 

[Randy Holmes-Farley]

I am not aware of much data at all that bears on the significance of phosphate stability, as opposed to average values or once a day measurements. I tend to think that variation in phosphate within a day is not an issue.

IMO, if it is measured at any time to be less than 0.03 ppm, I'd feed more or dose phosphate.

 

[george9]

I am not aware of much data at all that bears on the significance of phosphate stability, as opposed to average values or once a day measurements. I tend to think that variation in phosphate within a day is not an issue.

IMO, if it is measured at any time to be less than 0.03 ppm, I'd feed more or dose phosphate.

I’ve been diligent about checking daily to make sure I am not reaching the danger zone any more, because once I go below .03 the change in coral coloration is pretty rapid, noticeable in less than 24 hours. On the other hand, I have not noticed a change in coloration or PE when I overshoot my target, like today for example at .14ppm.

I suppose as long as I am not approaching .2-.3 range (which is pushing it for sure), I will not worry if corals appear healthy.

 

[Waters]

When it comes to intake of nutrients by coral, I don't think stability (of phosphates and nitrates) is that important. If it is available for the coral they use it. Whatever they don't use, remains in the tank. As stated, it only becomes an issue when there is none available. Obviously super high numbers of either aren't good but this is more about stability at normal levels.