What is DKH, I haven't seen a test kit for it. I've had a nano for 6 months and I just got my 135 gal set up 2 months ago and everytime I turn around it seems I have to buy a bottle of something! Purple-up, success calk, strontium, magnesium, I have 5 different bottles in the stand under the tank, DO I NEED ANOTHER? What about a PH buffer? My ph has always seemed to be within limits, but then again After testing nitrate, nitrite, ammonia, phosphate, calcium, alkalinity, I get alittle tiried of testing!!!!! All this Chemical stuff is making my head spin!