Ok so I have a high light high tech planted tank that is showing what looks like a calcium deficiency. I use pressurized co2 with an almost yellow drop checker, and it's spot on for 30ppm using the ph/kh chart, also if I bump up the co2 slightly the fish start showing stress. I maintain around 30ppm of nitrates and 2ppm of phosphate. I add 20ppm of potassium weekly. Water change is 50% weekly. I dose CSM+B twice weekly to maintain iron at .5 ppm. This is where things get weird. Out of the tap my water has a kh and gh of 0 degrees, my taps TDS is 35. My tank measures 10dgh and 6dkh. I was not adding any calcium or magnesium. The kh and gh gradually climb over the course of a week even when not adding anything. On a hunch I took a sample of my gravel and put it in a glass with a little vinegar and a few pieces started to fizz
The gravel is from petco and it's the river gravel, it claims that it wont affect water chemistry. The pieces that fizz are gray colored, making me think that maybe its magnesium carbonate? I have tried using equilibrium to up my calcium some, but it also adds magnesium and potassium. I just ordered some calcium sulphate and I'm planning a large water change and dosing 20ppm of calcium. The deficiency definately looks like calcium, twisted growth, cracked light colored leaves, and tip burn. Tank is 25 gallon, lights are 62 watts t5ho on for 7 hours a day. Plants affected are amazon sword and hygrophila carymbosa compact. Strangely the water wisteria seems unaffected. I do use flourish root tabs for the amazon and carymbosa. What do you guys think, could this be a case of excess mag blocking calcium uptake? Thanks in advance for any insight.