When to test for P04?

[dubmaneh]

I have been testing P04 in the morning before lights on, and at the end of the day before feeding to get a better understanding of consumption rates.

P04 ranges from 0.211ppm in the am (before lights on) to 0.055 in the pm (right before feeding and lights out).

When should I be aiming for the >0.03ppm number?

If P04 drops to undetectable, bad things happen.




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[Tripod1404]

I would average it out. Also keep in mind >0.03ppm is a pretty subjective number number. Ideal PO4 levels depends on the lighting and alkalinity levels.

[bertoni]

That range is very broad. I'm surprised it's that wide. What are you using for testing?

[Subsea]

I run high nutrient systems that support filter feeders and sponges.

I never check for phosphate. Cynobacteria is my bioindicator for phosphate.

[dubmaneh]

Originally Posted by Tripod1404

I would average it out. Also keep in mind >0.03ppm is a pretty subjective number number. Ideal PO4 levels depends on the lighting and alkalinity levels.

Good point. I quoted >0.03ppm as it seems to be referenced in a number of places for SPS growth/colouration. Looking at my notes, I had some of my best growth when I was getting readings of 0.14ppm

Originally Posted by bertoni

That range is very broad. I'm surprised it's that wide. What are you using for testing?

Im using a Hanna ULR.

Originally Posted by Subsea

I run high nutrient systems that support filter feeders and sponges.

I never check for phosphate. Cynobacteria is my bioindicator for phosphate.

Nice tank!

[dubmaneh]

Thanks for the feedback. Got me looking differently at my notes and I think I figured it out.

On the whole the P04 levels have been slowly rising but fairly stable regardless of time of day. There were a few readings that seriously bucked the trend which threw me off. They can however attribute these to various events.

My lowest reading of 0.006ppm came after doing a 20% water change. The highest reading of 0.211ppm came the morning after introducing a new food (P04 dropped to 0.055ppm that evening but I'd guess my rocks/algae/corals soaked up the excess!).

If I exclude the anomalies, average readings come in at 0.0353ppm in the morning and 0.452 in the evening, which seems to make little more sense.

[bertoni]

Since you're trying to keep the phosphate level above 0.03 ppm, I think testing at the daily low point would be the best approach.

[dubmaneh]

Originally Posted by bertoni

Since you're trying to keep the phosphate level above 0.03 ppm, I think testing at the daily low point would be the best approach.

LOL! I meant to post <0.03ppm! But yes, that would make sense. I was confused about the fluctuations as I didn't think it should fluctuate that much. Thanks.