More pH problems
 

I posted here a few weeks ago about issues with my water and my two dead cories. :( So my stats as of right now...I've got a betta in a 2 gallon bowl waiting to be transferred to the 10 gal. The 10 gal has only been cycling for a week, but I'm not seeing the results I expected to see with a fishless cycle. I completely redid the tank because of the bizarre problems with pH I was experiencing. I now have new gravel, the same plants, the same filter, and the same decorative thing. Last Saturday I poured out the old gravel and rinsed out the tank with hot water. Since I didn't want to kill all of the bacteria I've cultivated I skipped rinsing the decoration. I put everything back together with the new gravel and tested the water levels. A week ago ammonia was 0.25, nitrite 0, nitrate 0, pH 7.6. All of this was tested with the API liquid master freshwater test kit. I tested the water on Sunday and got the same results and Monday the ammonia was up to 0.5 but I think that's normal for tank cycling. I didn't test for a few days and today I tested again and ammonia is up to 0.75 ish and pH is down to 6!!! This is the exact same thing that happened last time. What am I doing wrong? Should I get a completely new filter cartridge?

I don't think you should worry about your ph until the tank has finished cycling. Once the cycle is done and the tank is stabilized, then you can see where the ph is and adjust as necessary.