All this Hobby-Stuff is not professional!
I use at least MERCK chemicals or electronic devices, like an Oxymeter or photometer.
It just should be a productline of a professional Chemical company.
I tested Sera, Tetra and JBL and did not get any objectively valuable result.
If it is not the insufficient configuration of those products, then the storage in petstores might harm the chemicals quality.
For professional results you will always need professional products.