Nitrates stable but phosphate down?

[peterhos]

Morning Everybody. I recently replaced the RO filters and have also increased water changes slightly - now doing around 13% a week. 4 days ago an ICP test showed phosphate at 0.24, today Hanna checker showed 0.09 and 0.13 on a second test. Nitrates with Hanna checker have been showing around 24 2 weeks ago, down to 21 today. So, proportionately my phosphate has fallen faster than the nitrate. Can that happen? Yesterday I shook the in-sump media bag that contains around 3 tbs of Rowaphos. Could that explain things? Thanks for any thoughts.

 

[Randy Holmes-Farley]

I would not try to track phosphate changes between ICP and home testing because many things happen between collecting the sample for ICP and testing the sample that can alter phosphate.

ICP also detects more forms of P than does a phosphate kit, so can be expected to read at least as high, and sometimes higher, than the home kits.

I'd just keep monitoring with the Hanna.

 

[peterhos]

I would not try to track phosphate changes between ICP and home testing because many things happen between collecting the same for ICP and testing the sample that can alter phosphate.

ICP also detects more forms of P than does a phosphate kit, so can be expected to read at least as high, and sometimes higher, than the home kits.

I'd just keep monitoring with the Hanna.

Good point. Thank you Randy.

 

[jda]

Most ICP companies are doing acetic acid po4 test on orthophosphate just like you are. What Dr. RHF is saying is that there are other types of phosphates that might not show up on an acetic acid test when first put into the tube, like Metaphosphate, that can turn into orthophosphates in the days following.

Some ICP companes (not all) use total P test kits that turn all forms of phosphate into Ortho before testing. They report these as total P. Some companies take the results of an orthophosphate test and multipy them by about 3 and call this P. These are like apples to volkswagens.

I could be wrong, but I don't think that any ICP companies use the plasma on this.

In any case, in home is better than ICP for po4, IMO.

 

[peterhos]

Most ICP companies are doing acetic acid po4 test on orthophosphate just like you are. What Dr. RHF is saying is that there are other types of phosphates that might not show up on an acetic acid test when first put into the tube, like Metaphosphate, that can turn into orthophosphates in the days following.

Some ICP companes (not all) use total P test kits that turn all forms of phosphate into Ortho before testing. They report these as total P. Some companies take the results of an orthophosphate test and multipy them by about 3 and call this P. These are like apples to volkswagens.

I could be wrong, but I don't think that any ICP companies use the plasma on this.

In any case, in home is better than ICP for po4, IMO.

Again, thank you. I did not know that.