Burmeseanswered grow question 3 years ago Hi there, I use egg shell dissolved in vinegar as my pH down solution.Not only as pH down but also as calcium supplement for my plants.I dissolved 50~100g of egg shell in 500ml vinegar and apply 0.5~1.0ml per liter of water.Adjust pH as necessary and my plants are all healthy and green.I think You can use to lower your pH in that way.Good luck and happy growing... ✌️