How long after dosing silicates is phophate testing reliable ?

[Idech]

Do you use UV?

Edit: sometimes UV is the only thing that can knock it down for good.

Yes I do, 24/7

 

[Idech]

What does unreliable mean to you?

It means the result are at least 2-3x higher when there is silicate in the system. When the silicate dies off after x number of days/weeks, the results are considerably lower.

This did not happen once. It has happened consistently over 2 years, every time I tested. So I rarely do anymore.

 

[Randy Holmes-Farley Verified Community Expert]

It means the result are at least 2-3x higher when there is silicate in the system. When the silicate dies off after x number of days/weeks, the results are considerably lower.

This did not happen once. It has happened consistently over 2 years, every time I tested. So I rarely do anymore.

It could be silicate interference, or it could be phosphate in the silicate dosing solution. :)

 

[Idech]

It could be silicate interference, or it could be phosphate in the silicate dosing solution. :)

What is silicate interference ?

And how do I know if there is silicate in the solution ? Any way to test ?This must be very commun though because so many people are having this problem too.

 

[Randy Holmes-Farley Verified Community Expert]

What is silicate interference ?

And how do I know if there is silicate in the solution ? Any way to test ?This must be very commun though because so many people are having this problem too.

What problem are people having?

Silicate can react with the reagents in a phosphate test a way similar to phosphate, showing more phosphate when it is there. It generally takes a lot and only typically is a concern when dosing silicate.

 

[Idech]

What problem are people having?

I haven’t investigated any claim, but if you go on reefing groups on FB, this regularly comes up. People are wondering why their phosphate readings on their Hannah ULR checkers are so high when dosing silicate.

 

[Randy Holmes-Farley Verified Community Expert]

I haven’t investigated any claim, but if you go on reefing groups on FB, this regularly comes up. People are wondering why their phosphate readings on their Hannah ULR checkers are so high when dosing silicate.

It could be for either of the reasons I mentioned above. How significant either is depends on how low of a phosphate level you are trying to maintain and measure, and what kit.

If you haven’t read this thread, I’d suggest doing so:


https://www.reef2reef.com/threads/high-silica-interference-with-po4-measurement.777022/

 

[Miami Reef]

If you dose under 2ppm silica, the phosphate increase is clinically insignificant. This is based on numerous tests with different experienced users using silicate.

If you get a phosphate rise from dosing under 2ppm Si, then the silicate solution contains PO4. IMO.

 

[Reef-Engineer]

Ok so I think I agree with Miami and Randy at this point and that is to say that one must be critical of Hanna Phosphate ULR results for some time after dosing a silica solution to the reef. This may be due to interference from the silica itself depending on your dose, or it may be due to phosphate in the product. Either way, don't believe your checker when it reads 10x your normal level in these conditions.

That being said, my phosphate was right back at the normal levels as measured within 48hrs. I feel like phosphate added to the system in great quantity may dwell longer than that, so I felt as though in my case Silica interference was more likely. (all anecdote, would require testing to prove)

Closed book for me, since in general to the masses here it doesn't matter if it is phosphate in the solution or the silica interfering, the answers is the same, get a different test kit or don't trust your checker when dosing silicate presumably to fight dinos or grow sponges.

 

[Radon]

Does anyone have a definitive answer as to when one would be able to use phosphorus ulr checker after dosing silicates? I’m still seeing some diatoms mixed in with green algae, it’s been a few weeks.

 

[Randy Holmes-Farley Verified Community Expert]

I think that was clearly answered by Miami: any time. The interference is very low. See Miami’s Post 2 posts above.