Hard water low ph
I have a 92 gallon planted freshwater tank. My tap water ph is 7.6 My tank parameters are gh 180, kh 40, ph 6, nitrite is now 1 and nitrate is 40, my ammonia is now .25. My tank has been up for 5 months I have sand substrate with gravel around the edges, a fluval 406, 5 airstones and a lot of plants currently my fish are: rubber nose pleco, 5 glass cats 3 cories, 4 angels, otto, scissor tails 2, danios 3, 4 neons, serpea tetras 7. Why is my ph so low I have added coral to the filter and after a week my ph still is only 6.4. I currently have a large snail issue. I want a clown loach but am worried about the ph as the lps water is 7.2.