I would suggest that you forget about the test kit, but worry less about cleaning your filters twice a week. The bacteria that inhabit your filter and are responsible for the nitrification process are not fast reproducers (I speak as a microbiologist). Many people have the impression that bacteria double in number every 20 to 30 minutes - yes they do if they are some of the fast growing pathogens in mammals at temperatures around 37C. Not our filter bacteria which grow at lower temperatures and utilise inorganic materials as a source of energy. You might be lucky and have them double in number every 2 to 3 hours. The consequence of washing your biological filter medium so frequently is that you are washing some/many off the surface (not inside the pores) AND you are removing the sludge/mulm which also contains many of these bacteria.
Cleaning/replacing the mechanical filter material such as matting every couple of weeks is fine, but cleaning the biological every 3 to 6 months, depending on the fish load, is more appropriate.