

What am I doing wrong?
So I set up my mom’s tank (first photo) about 3-4 months ago and she’s been keeping snails, shrimp and plecos. Alllllll of her snails shells look amazing no deterioration or anything. My main tank (second photo) I’ve never been able to keep snails and have them have a healthy shell. Everything from her tank is from my tank literally everything is the same but her tanks PH is 7.8 and mine is 6.4. What is going on in my tank that’ll get the ph low and how do I fix it? I absolutely love snails and I’m upset I can’t keep them. I’ve tried cuttlebones, I have a airstone in. I don’t have any stones that’ll make PH lower in fact I have elephant stone that should actually raise the ph so I’m really at a lost. Any advice?