[Peter Finke]

O, that’s a pity Merck doesn’t sell that germ-test any more. But there was another, similar test by another company; I’ll try to get the details.
The Hanna-instrument is high quality; I have it myself. But in order to measure the right pH-value it’s up to you to calibrate it from time to time (and you need the calibration-fluid that is sold by Hanna for that purpose). The you will receive very exact data. You must also take care for the sensitive electrode which does not like to be stored dry; they sell a storage fluid for that purpose. But any water is better than air.
Then your setting is quite good. I don’t think you really need the UV-equipment; I should omit that. You must always realize that there are “bad” and “good” bacteria. With that UV-filterung you cannot distinguish between the two groups; you kill them all. And that’s in most cases of no use, but the contrary. UV-filtering is the last escape only from very dangerous infections, nothing for permanent use in an aquarium. Even not a blackwater aquarium.
But since we are here a site especially for Parosphromenus and chocolate gouramis mostly co-exist in the same habitats as they do, we do not speak here of special measures for chocolate tanks, but for well-planned, well-cared tanks for small blackwater-fish. Therefore this issue was and is quite adequate in this frame-setting, for it is on good living conditions for Parosphromenus, too. The only major difference I see is that chocolates do not as well in very small tanks that suffice for the licorice.