testing for Iron

[DaveJT]

I'm interested in testing for Iron in my planted tank. I'm pretty sure I have a deficiency and will be supplementing Iron shortly and thought it would be interesting to test on a regular basis to quantify results a little.

However,

I did read a note from one of the hosts of a popular planted tank site that "All iron tests for aquariums are inaccurate and not to bother with them".

So ... Why might he make this claim?

Are there varying water conditions that alter the test? Are the many different types of Iron that can be added to the tank responsible for inaccuracies?

Are there different types of Iron tests? Which is preferable.

And of course... How, if at all does this pertain to SeaChem'S Iron test kit.

After Adding Flourish Iron to the tank will this produce a measurable response on SeaChem's Iron test.

Thank you.