I have had few problems with Dwarf Sag and my KH is <1 dKH and GH is <3 dGH. However, I recently had a problem where my Dwarf Sag started to thin out (was a thick carpet), beginning with leaves becoming transparent. I thought it was nitrogen, since it didn’t turn yellow. At the same time, I had also embarked upon a nutrient reduction program. In doing this, I had forgotten that Dwarf Sag is an iron hog. I began adding, now, about .5 ppm daily (I have a high-tech setup) and have had full recovery with it filling-in again after about three weeks.
You might want to try adding an iron supplement for a month or so to see if it helps. I’d start with .2 ppm 3-4 times a week.
It would also be interesting to know what your NO3 and PO4 readings are. There may be a clue in those.
Do you have good circulation?
I wouldn’t worry about dimming the Stingray. It is already a low-PAR light.
Incidentally, if your pH is 7 and your KH is 3 dKH, then your CO2 is about 10 ppm. It might be better to do the 1-point pH drop test:
Let some tank water sit out for a day or two to de-gas. Then measure the pH of your tank after CO2 peaks and compare it to the water sitting out. If you get a 1-point pH difference, then you have about 30 ppm CO2.
Last edited by Deanna; 05-13-2019 at 02:21 PM.