Hi there,
The Tetra 5 in 1 is saying:
1) Nitrite (NO2) (one of two poisons to fish) is zero, which, with fish in, is good news.
2) pH is 8.0 and KH=15 - A pH of 8 is fine for many fish and good for growing the right filter bacteria. Not sure whether the the KH on those strips is german degrees of hardness or mg/L, which would make a difference interpreting the KH.
3) Nitrate (NO3) at 10 is fine, nice to be low but not something that is worried about until quite high
4) GH - general hardness is not a measurement that we take any action on
BUT, the bad news is that many on TFF have reported that various of the 5in1 strip tests are not at all reliable as compared to liquid tests, so the general advice here is that they should be thrown out and one should definately obtain liquid-reagent based tests. (I myself bought a box of these same Tetra strips and haven't been able to make myself actually throw them out but I don't use them anymore, I only use liquid based testing kits.) Most aquarists here use the API Freshwater Master Test Kit or the european Nutrafin Mini one that has a nitrate test included. You'll note that the strips somehow don't have an ammonia test, perhaps the most important of all tests if one could make that comparison.
~~waterdrop~~
