Recommendations for a water Hardness test ?

I've used API GH/KH liquid, gives GDH by the number of drops needed to change color(german degrees of hardness) & the 5 in 1 strips gives ppm for GH & "alkalinity"(KH) by matching color to arange chart. You can get ppm by multiplying GDH by 17.9 (ish) or the other way. The API is probably more accurate.

Salifert would be the best test to get but for most general FW purposes the API liquid kit is good enough. Unless you're doing Discus or something then I'd drop the extra money for the Salifert.