Hi,
Yes, it is a well known fact that the whole point of EI is that you don't have to test. What is much less well known is the fact that testing tells you nothing because the hobby grade test kits are generally completely useless because they lie atrociously. So if you test for NO3 PO4 and Fe even though you are dosing per EI then you are only fooling yourself into thinking that you actually know what's going on as regards the nutrient levels. Test kits are also very expensive so there is no point spending £10 to as much as £30 for kits that tell you nothing. The performance of the plants and the status of algae in the tank are your test kit. If you see an algal bloom in the tank but if the test kit tells you everything is OK, which should you believe?
I can't even imagine a reason to test for K, which is the least controversial of the macronutrients. I can understand the proliferation of snake oil NO3 and PO4 kits because The Matrix has programmed everyone to fear these nutrients, but K has not been directly or indirectly implicated in any failure mode.
In any case, if you like spending money, and if you just like testing for the "fun" of it, then contact The Lamotte Company as they have K test kit - Product code 3138 KIW
Lamotte Individual K test kit. This is a direct reading titrator, where you determine the concentration based on the turbidity of the solution. I think they also have supposedly more accurate calorimetry tests but then you'd have to buy the calorimeter (£££). Not sure regarding UK distributors. You can also contact
FishVet, again I'm not sure regarding UK distribution.
Cheers,
