Phosphate Absorption of Aragonite Over Time

[Randy Holmes-Farley]

I’d suggest halting any experiments and replacing the tripolyphosphate with normal orthophosphate, such as trisodium phosphate, it likely has different (likely stronger) binding to aragonite and will test differently.

 

[jda]

Wait, phosphate is not phosphate once it breaks down and stuff? Which one is more like the po4 in a reef aquarium - I want to test that.

 

[Rick Mathew]

Rick - all that you said was correct. The values just keep rising over time and I wanted to see when they would stop. I am currently at .5ml in the 10l. I am going to test again tonight. ...so we should be around 85 ppb if your math is correct, give or take, when it is all said and done? Unfortunately, my tool stops at 200 ppb, so I am limited.

I was able to determine that the container and pump are at least phosphate free and that no phosphorus was detected after about 48 hours of fresh seawater just running through the container.

I just want to get a baseline so that every time I add X mls, I know that I added about Y of phosphorous.

Thanks for the clarity...If you keep getting the "blinking 200" try only putting 5 mL test water in vial and add 5mL of your "0" P water....do the measurement and multiply the value by 2...should be in the ballpark...I would follow Randy's and Dan's advice and switch reagents..

 

[jda]

Thanks for the clarity...If you keep getting the "blinking 200" try only putting 5 mL test water in vial and add 5mL of your "0" P water....do the measurement and multiply the value by 2...should be in the ballpark...I would follow Randy's and Dan's advice and switch reagents..

I just did this and it came out to 160.

 

[Rick Mathew]

I just did this and it came out to 160.

So is that 160 X 2= 320 or 80 X 2=160

 

[jda]

I used 5ml of fresh saltwater and 5ml of the stuff in the container for the Hannah test which came out to 160. 320 total. Sorry about that.

 

[Rick Mathew]

I used 5ml of fresh saltwater and 5ml of the stuff in the container for the Hannah test which came out to 160. 320 total. Sorry about that.

No worries...That is a lot of phosphorous!!...That amount does not jive with the solution you made of 10 g/500mL water...at least by my calculations...I think as you mentioned you need a "regroup" I would start with trisodium phosphate---

Make a standard solution from that...

 

[jda]

Where does the 3.066 conversion from po4 to phosphorous fit into all of this?

 

[Rick Mathew]

Where does the 3.066 conversion from po4 to phosphorous fit into all of this?

So as I understand it you are using the HI-736 ULR Phosphorus Checker. THis measures Phosphorus in ppb...To get PO4 in ppm you need to take the meter reading of the HI-736 multiply it by 3.0661 and divide that value by 1000 to get ppm PO4...If you want the PO4 value in ppb don't divide by 1000

so using your value of 320 ppb P you would get .981 ppm PO4 or 981 ppb PO4

Hope this helps

Rick

 

[Randy Holmes-Farley]

Wait, phosphate is not phosphate once it breaks down and stuff? Which one is more like the po4 in a reef aquarium - I want to test that.

The issue is that we do not know how long it takes tripolyphosphate to break down into individual phosphate ions, and that may impact both the testing and the binding.

 

[92Miata]

So as I understand it you are using the HI-736 ULR Phosphorus Checker. THis measures Phosphorus in ppb.

Sorry - this is nit-picky as hell, but it bothers me for some reason. SO just carry on and ignore my pedantry if you're looking for something useful.

The HI-736 uses the ascorbic acid method, which is specifically a test for orthophosphate. It does not measure phosphorus. It measures orthophosphate, and then does a lossy conversion/calculation to display ppb phosphorus.

So it's meter measures phosphates -> calculates phosphorus (lossy) -> user converts back to phosphates(lossy)

 

[Rick Mathew]

Sorry - this is nit-picky as hell, but it bothers me for some reason. SO just carry on and ignore my pedantry if you're looking for something useful.

The HI-736 uses the ascorbic acid method, which is specifically a test for orthophosphate. It does not measure phosphorus. It measures orthophosphate, and then does a lossy conversion/calculation to display ppb phosphorus.

So it's meter measures phosphates -> calculates phosphorus (lossy) -> user converts back to phosphates(lossy)

Stand corrected...Learn something new every day...thanks for the insight....not nit-picky at all...

Rick

 

[Randy Holmes-Farley]

Sorry - this is nit-picky as hell, but it bothers me for some reason. SO just carry on and ignore my pedantry if you're looking for something useful.

The HI-736 uses the ascorbic acid method, which is specifically a test for orthophosphate. It does not measure phosphorus. It measures orthophosphate, and then does a lossy conversion/calculation to display ppb phosphorus.

So it's meter measures phosphates -> calculates phosphorus (lossy) -> user converts back to phosphates(lossy)

I don't know that mathematical conversions are lossy, but its certainly a marketing gimmick of no actual utility.

 

[jda]

The issue is that we do not know how long it takes tripolyphosphate to break down into individual phosphate ions, and that may impact both the testing and the binding.

It takes about three days in saltwater with a pump... if it ever comes up in a Chemist mostly-useless trivia night at your local Bar & Grille.

 

[juarec0201]

I think this is the root for a huge chunk of new tank dino outbreaks. No one is telling new hobbyists to be prepared to dose phosphates and ensure it doesn’t bottom out while their dry rocks are soaking it all up.

This was the cause of so much growing pains. I was under the assumption low phosphates was good. Didn’t realize bottoming our would kill coral fast. Have had multiple crashes due to bottoming out and still have to dose weekly

 

[jda]

Off topic, but I doubt that low orthophosphate readings in a newer tank had much to do with any losses. Not only do I run about 1 to 3 ppb in my tank, which is more than the ocean, I have been reading a lot and organically bound phosphate and metaphosphate are what most micro algae prefer. Stopping import is a bad thing since not only will it bottom out readable po4, it likely bottoms out other sources as well.

I have more to read and study, including some stuff in different languages which can be hard, but it appears that what the Hannah tests for is the least helpful thing except to poison/growth-limit dinos, cyano and diatoms.

In the end, high available phosphorus is a good thing with low residual levels of phosphate. We cannot even test for most of this, so just feed your fish heavily and export heavily and you will be fine.

 

[vahegan]

To eliminate other factors except for deliberately added phosphorus, I would rather start the experiment differently:

• start with the system filled with pure saltwater and no aragonite and no added phosphate. Test daily for a few days.
• add aragonite to the reactor, but no phosphate. Run for a few days, test daily
• once make sure that the system is stable and there are no significant changes in measured phosphorus, you can start dosing.

Since your meter is not able to distinguish anything over 200ppb, I would start with much smaller doses, maybe 1/10 of what you used. Then, based on the results, you can adjust the dose.

 

[jda]

I already did the first two things. Stayed at zero for 3 days with just water in the bucket with the reactor and pump. I got like 0, 1, 0 and 0 when I added the aragonite into the mix. While not all 0s, pretty close and well within range of the tester.

I might pause on this for a while. After reading a lot, it seems likely that metaphosphate from fish waste or some other decomposition is what most corals are after and that ortho is the residual byproduct of what is left behind from some other process that does not benefit most micro algae, or is at least not preferred. Since my focus is on true coral with zoox, then this is what interests me. I need to read a lot more to see if I can frame a test that reflects something that corals can use.

I did find out that it takes about 3 days for metaphosphate to stop becoming ortho. Somewhere between 32 and 36 hours on the 3rd day, the levels stopped rising and rose no more for the next two. This three day window might be when an inorganic source of phosphorous is most available to corals to use. Of course, organically bound phosphorous is always a welcome source.

For a long time, many successful reefers have suggested heavy import and heavy export with low residuals to be the best for coral, suggesting that there is a small window where ammonia is providing nitrogen and many different forms of things (organic/inorganic phosphorous/phosphate but nobody was such which was better) are delivering phosphorous. Ocean, too, right... stuff thrives with only traces of measurable no3 and po4, but do not appear at all to be nitrogen or phosphorous deficient. This jives, so far. We pretty well know that measuring no3 might be fools gold and it appears that measuring po4 might be the same.