Ph Too high

[NewOne81]

I have a 4gal reef tank about 2 1/2 months old. My ph seems to being reading high on my api test kit.

Readings in the evening are 8.6-8.7 and mornings 7.8

Recent Tank additions were 1 skunk shrimp, 5 snails and a torch coral.
Other residents are 3-4 hermit crabs

Had 1 clown fish which died do to ph i believe

I do weekly water changes of about 20%

Ammonia 0
nitrite 0
nitrate 0

in an act of desperation i added proper ph 8.2 as a temp fix but doesnt seem to be making a difference. Corals are somewhat closed but all else seems fine. My mixing water ph before salt is 7.2ish. After mixing to sg 1.025 it reads 7.8 and tank reads 8.6-8.7.

Any ideas what might be going on here as im out of ideas

[Percula9]

I doubt your pH is that high. A chemical pH test kit can be problematical. I would get a pH meter to verify. A 4gal tank is not a lot of tank to work with. What is the alkalinity?

[NewOne81]

dont currently have a test for that

[Percula9]

Then get one. API makes one as costs around $7.99-8.99.

[bertoni]

7.8 at night isn't that bad, if the number is accurate. pH buffers are high-pH alkalinity supplements, and can cause a wide variety of problems. Plus, their effect tends to be very temporary. The cause of true low pH is a high indoor carbon dioxide level.

I'd get an alkalinity test kit and a second opinion on the pH test kit before doing anything. Also, I'd stop the Proper pH.