Is there an easy way to add calcium without increasing ph? My water tests 7.2 am, then 6.2-6.4 pm after 10 hrs of pressurized co2. Gh/Kh are 5/8. Have gotten better growth recently by adding Epsom Salt, so adding some calcium too might help, but not sure if I'd want the ph to go up. I saw Plaster of Paris mentioned here. Would that work? Thanks.