I know I am probably stating the obvious, but ...... (I don't mean to be offensive) When you do your water changes do you have a bucket / equipment that is exclusively fishy? I grabbed my water change bucket one time and found a white/chalky substance in the bottom. She said "I only used it one to wash the floor".
Yeah it looks like you need to be cleaning your tank more and doing more water changes...I recommend water changes of 50% a week if not more and those rocks and plants look completely taken over by algae or cb.
I suspect you can't get a reading for GH because it's unmeasurably low. The end point and start point colours can be rather faint at very low concentrations.
Like I said prev, dilute the samples with distilled water (1:1, 1:2, etc, etc) to check if GH kit is rendering correct #.
pH/KH/GH of tank before/after water changes as well as of tap??????
If pH kit renders 6.0, it could be lower than that for all I know. Make sure there is no presence of NH3/NO2 at such pH before and after wc.
I could presume few possibilities but W/o further info/datas, hard to say exactly why at this point, imo.
Provided GH test kit is working, if color didnt change after so many drops, I stroongly doubt GH is low as one or few drops drops shoulve changed the color if GH was low enough..
I don't think stress coat is a dechlorinator... my guess is that's the problem. Try treating your tap water with Prime or Nutrafin Aqua plus. (I'm a big fan of the Nutrafin but I've heard excellent things about the Prime.)
I usually let my water sit in a bucket after adding the dechlor for 5-10 mins to make sure before I add to the tank but you could probably add it straight in.
whoa the test kit i uses says that you add test liquid one drop at a time until sample turns yellow where are you reading that you keep adding until it turns green??????????????????????????????????