Buffering water to achieve higher ph

The water where I am is incredibly soft. At the moment it's a ph of 6.6. Kh is 1 drop to change colour which is 1°. Gh is 4°

I have rabbit snails which prefer a much higher ph and an acidic ph is a no go for snails. Ph from the tap can range from 7.2 to 6.6. So I have crushed coral in the filter which raises it to 7. That's been in for say 9 months and this week I noticed the tank ph dropping. So I replaced all the crushed coral with new. I had to add bicarbonate soda to raise the ph by 0.2 each day until it was 7.2. The ph has no dropped to 7. Will the crushed coral take a few weeks to have an effect? Is it normal to have to replenish it? And how can I get my ph to 7.2 or will 7 be ok? The amount I have in my filter is all I can fit and it settled at 7. I also added a couple of small limestone rocks to the tank as well

 

It sounds like you touched all bases.
Maybe construct a more substantial limestone hardscape.
I have over 200 lbs. of limestone in my African tank & about 70 lbs. of it in my Barb tank. The PH stays locked at 8.2. The water in my area is already hard w/ an elevated PH, so the limestone has little effect.

 

Will the crushed coral only buffer it to 7 or would adding more raise it higher?

 

The more coral & limestone added to the system, the higher the PH will go.
Most FW setups won't exceed a PH of 8.2.

 

I'm happy with 7.2. Or 7. I feel chasing a ph is very difficult to get right. I have to add tiny amounts of baking soda when doing a water change. Will it take a few weeks for the crushed coral to kick in and raise the ph?

 

Adding the baking soda & continued use of the crushed coral looks to be the best route for you to go.
Subtle changes in PH shouldn't disrupt your setup.

 

It's frustrating. The crushed coral is the most stable option and it's worked for nine months. I just know I need to replenish all the crushed coral every six months or so. Its finding a balance. I am setting up a small nano tank for red cherry shrimp so that will be a task to keep stable with it being smaller