foxfish said:
Thanks for the answers & discussion.
I wonder how this debate would fair on a more fished based forum like PFK, no doubt many thousands of folk rely on test kits as part of the hobby!
When discussing test kits I think it’s important to differentiate between ‘general’ fishkeepers and planted aquarium owners.
In a non-planted tank there’s little or no nutrient export except via water changes and/or chemical adsorption. Perhaps there’s de-nitrification in some circumstances.
For this reason in a non-planted tank it may be more prudent to rely on test kits to measure things like NO3 and pH regularly. These are a good indicator if your maintenance regime is effectively dealing with the waste build-up. The same with PO4 kits.
Although kits themselves may be inaccurate they still have their use in these types of aquariums for spotting trends.
Actual ppm (mg/l) levels aside, it’s fair to say that a NO3 test kits results will show the fishkeeper whether their nitrate levels are on the up or not if they test regularly using the same kit. If the NO3 does increase over the weeks then it’s time to change more water, give the substrate a better clean, or maintain the filter more frequently.
The same principle can be applied to a drop in pH, which is commonly associated with excess organic build-up. High nitrates and low pH are classic symptoms of “old-tank syndrome” and test kits are a good indicator to help identify this.
KH and GH test kits are also a good indicator of roughly how hard your water is so you know whether it’s appropriate to keep Rift Valley cichlids or wild-caught discus (although a TDS or conductivity meter may be more appropriate).
Obviously most modern planted aquariums are fundamentally different and the consequent nutrient management through plants growth, nutrient dosing, and water changes renders testing almost redundant, except for pH and hardness when choosing appropriate livestock.
I also advocate the use of KH3/4 and NO3 kits when stocking for the first time after using new Aqua Soil-style substrate.
In summary test kits have their place but IMO shouldn't be relied upon in a planted tank to determine exact parameters. They can be useful to perform basic trend analysis and to determine baseline parameters for tap water.
my main concern is for the thousands of folk who not only rely on test kits (matrix effect) but insist upon there use..... I mean look at any fish keeping forum (including this one) & you will see hundreds of post empathising just how important it is to test your tank water & your tap water.