How long after dosing silicates is phophate testing reliable ?

[ryshark]

Okay, I just tested and here are the results :

Nitrates (Hanna) : 12 ppm
Phosphates (Hanna) : 0,9 ppm
Phosphates (Salifert) : 0 ppm (it must be a little above 0 but this test is not very precise.)

0.9 or 0.09 ?

 

[Idech]

0.9 or 0.09 ?

0,9. The previous test was 0,42.

Here is a whole thread about it. It seems to be an issue with Hanna checkers when dosing silicate.

Phosphorus ULR and high silicates

Hi, Is it possible that the Phosphorus ULR checker can inadvertently detect silicates when they are at extremely high levels? I recently added Siporax media to my sump and I know these release very very high levels of silicates for the first couple of weeks. My checker has been detecting...

www.reef2reef.com

 

[Randy Holmes-Farley Verified Community Expert]

That is a tank water test?

 

[Miami Reef]

Maybe I dreamed all this, lol ! I’ll test soon and post the results.

lol

 

[Idech]

That is a tank water test?

Yes, reef tank water.

 

[taricha]

Alternately, here's a recent thread where PO4 was off-the-charts high (approaching 10ppm!) on two other tests, but salifert barely detected anything.
Maybe the salifert is just not working correctly. There's no reason to think there's a hanna specific Si interference, except that only hanna checkers are likely to detect the small interference of a few ppm Si.

 

[Idech]

Alternately, here's a recent thread where PO4 was off-the-charts high (approaching 10ppm!) on two other tests, but salifert barely detected anything.
Maybe the salifert is just not working correctly. There's no reason to think there's a hanna specific Si interference, except that only hanna checkers are likely to detect the small interference of a few ppm Si.

What would have caused that phosphate spike ? I went from 0,08 ppm phosphates to 0,42 ppm after dosing silicates for a few weeks.

How is that possible ?

 

[Randy Holmes-Farley Verified Community Expert]

What would have caused that phosphate spike ? I went from 0,08 ppm phosphates to 0,42 ppm after dosing silicates for a few weeks.

How is that possible ?

The daily additions of P from foods are enough to do that easily if uptake slows, and perhaps diatoms use less phosphate than green algae to cover the same surfaces.

 

[Idech]

The daily additions of P from foods are enough to do that easily if uptake slows, and perhaps diatoms use less phosphate than green algae to cover the same surfaces.

It doesn’t seem to apply to my case. Food input has not changed, neither has uptake. And I never had much visible green algae that I know of.

This is very puzzling to me. Now I’m scared my phosphate levels are really super high. Doing water changes and dosing less silicate might mean the return of dinos.

I’m really at a loss on what to do here.

 

[Idech]

Alternately, here's a recent thread where PO4 was off-the-charts high (approaching 10ppm!) on two other tests, but salifert barely detected anything.
Maybe the salifert is just not working correctly. There's no reason to think there's a hanna specific Si interference, except that only hanna checkers are likely to detect the small interference of a few ppm Si.

I read the thread and from what I understand, this person was not dosing silicate. They just had a faulty test. I don’t think it is a similar issue.

 

[taricha]

I read the thread and from what I understand, this person was not dosing silicate. They just had a faulty test.

I agree. Their salifert kit was giving false low value unrelated to any Si. Perhaps your salifert discrepancy also had nothing to do with Si.
I hate to say get another kit, but when hanna says 0.5 to 1 ppm PO4 and salifert says more like zero... then I'd get another kit. Any other new kit should be good enough to tell the difference between those two results.

 

[Idech]

I agree. Their salifert kit was giving false low value unrelated to any Si. Perhaps your salifert discrepancy also had nothing to do with Si.
I hate to say get another kit, but when hanna says 0.5 to 1 ppm PO4 and salifert says more like zero... then I'd get another kit. Any other new kit should be good enough to tell the difference between those two results.

You’re right. I just ordered the Aquaforest phosphate pro test kit.

I might get it tomorrow or Friday at least, I hope. I’ll keep you posted.

 

[Idech]

I’ve just tested phosphate with the Aquaforest phosphate test. Results indicate a very low value, close to 0 or possibly 0.

I’ll dose some Neophos in a small container of saltwater today and re-test, just to make sure it is valid. If I don’t see a different result, I will consider this test faulty.

 

[Idech]

I tested some tank water after adding a few drops of Neophos to a small amount of water and the results were off the chart, as was to be expected.

So that concludes this experiment; both the Salifert and Aquaforest tests tell me that my phosphate levels are very low, close to 0.

It doesn’t answer my question though : when will I be able to test with my Hanna checker ?

I’ll update this thread when I find out, lol !

 

[taricha]

I tested some tank water after adding a few drops of Neophos to a small amount of water and the results were off the chart, as was to be expected.

So that concludes this experiment; both the Salifert and Aquaforest tests tell me that my phosphate levels are very low, close to 0.

It doesn’t answer my question though : when will I be able to test with my Hanna checker ?

I agree that the Hanna kit seems to be giving incorrect results. I'm wondering if it's just bad, or if it's specifically bad because of the Si.

So are all of these true?
A) other kit reads low PO4 in tank water but is correctly responsive to a dose of PO4 (above post says yes)

B) hanna reads high PO4 in tank water while other kit reads near zero. (OP says yes)

C) hanna and other kit both read low PO4 in new clean SW.

D) dosing a couple ppm or so Si to the low PO4 new SW causes hanna to be nonsense high on PO4 while other kits stay low.

 

[Idech]

I agree that the Hanna kit seems to be giving incorrect results. I'm wondering if it's just bad, or if it's specifically bad because of the Si.

It’s my first Hanna phosphate checker, but it’s given my realistic results since the beginning. The tank was set up on October 4th 2021 and I bought the checker in December.

IMO the Si dosing is causing the problem.

Never mind the last value on this graph, it’s the one from the Salifert test.

 

[taricha]

IMO the Si dosing is causing the problem.

Unless the hanna reagents are just bad. Bad batches can occur.

BTW what is your Si source and how much are you dosing?

 

[Idech]

Unless the hanna reagents are just bad. Bad batches can occur.

BTW what is your Si source and how much are you dosing?

I’ve been through 2 batches of reagents and the results were always consistent with both. Nothing unusual.

This is what I bought. It’s 37,5% silicate (it doesn’t say on the website but they sent me the info sheet).

I dosed daily for 5-6 weeks - the first week around 2 ml and after that 1 ml. I stopped dosing since except when I did a 5 gallons WC (tank is 75 gallons) last week because I was afraid dinos would come back. I dosed 2 ml.

Sodium Silicate, N Brand – Sounding Stone

⚠️Warning! Sodium Silicate will freeze in cold climates! If sodium silicate has frozen, it will be ineffective as a deflocculant. We will only ship to cold regions in the winter at the customer’s risk. Water glass. Used as a major deflocculant in preparing slip. It reduces the amount of water...

www.soundingstone.com

 

[taricha]

ok so each 1mL dose of 37.5% SiO2 in 75 gallons adds 1.3 ppm SiO2 (0.6 ppm Si). That's as much as I ever dosed.
I don't think it'll accumulate excessively at that rate, but without a Si test it's hard to know for sure. In my system, that would have been a little higher than my daily SiO2 consumption rate.

 

[Idech]

ok so each 1mL dose of 37.5% SiO2 in 75 gallons adds 1.3 ppm SiO2 (0.6 ppm Si). That's as much as I ever dosed.
I don't think it'll accumulate excessively at that rate, but without a Si test it's hard to know for sure. In my system, that would have been a little higher than my daily SiO2 consumption rate.

I’ve read there are no reliable SI tests, which is why I never bought one. Do you know of any ?