phosphate

rayn · Oct 14, 2014

I am using a Hanna phosphate checker to keep track of my phosphate levels. I am wondering what test number to use. I can test twice and get two different results. Test a third and it may match the second or slightly off.

Last night...test 1---.08_____test 2---.03
Tonight...test 1---.05______test 2---.01

Which is accurate? I don't really want to blow through the reagent using two per testing period.

Randy Holmes-Farley · Oct 15, 2014

Which checker?

Both of them have a stated uncertainty that you should keep in mind, and that assumes perfect user operation.

The 713 has an uncertainty of +/- 0.04 ppm, so you cannot tell which of those values is more accurate.

The 736 has an uncertainty of about 0.015 ppm. If the real value were 0.02 ppm, you could get either reading.

rayn · Oct 15, 2014

Thanks Randy. It is the 713 I have. Maybe I need to break down and get the other one though. Phosphates seems to be one of my issues I continually run into, I believe it is leaching from my rock.

It is kind of disappointing though that a element we strive to keep low as possible, the tests aren't that accurate. Sure the 736 gets closer and most likely .015 won't matter, but I thought the other meter was better then .04.

Randy Holmes-Farley · Oct 15, 2014

Many people do assume the checkers are more accurate than they really are.

Why do you think you have a phosphate problem?

rayn · Oct 15, 2014

Current readings of my tank for phosphate are ranging from .01 to .08. Nitrate is at .3 ppm per red sea kit. I am still having hair algae issues, so it is getting used somewhere. I also just had a sps frag stn recently from the bottom up. After searching for that I read phosphate can be the issue.

Randy Holmes-Farley · Oct 15, 2014

rayn said:
Current readings of my tank for phosphate are ranging from .01 to .08. Nitrate is at .3 ppm per red sea kit. I am still having hair algae issues, so it is getting used somewhere. I also just had a sps frag stn recently from the bottom up. After searching for that I read phosphate can be the issue.

At 0.03 ppm or lower, the phosphate didn't cause the STN. However, it might have contributed if the value was substantially higher.

At the moment, it doesn't look like action is needed (IMO), but if you want to lower it or deter the algae, I'd use a phosphate binder, such as GFO, or possibly organic carbon dosing. I also grow macroalgae, but that will take longer to have a significant effect.