Cycling trouble

[Littleboo]

I've been out of the hobby for a few years and recently decided to come back. I set up a 55 US gal tank at the end of September and have been doing a fishless cycle. I've done it before but things don't seem to be going smoothly this time. I have a marineland penguin 350b filter, pool sand for substrate and I'm using the API liquid test kit. My cycle was going smoothly until Thursday. My nitrites had been quite high and and had finally began to drop to 0. But it seemed my nitrates, which had previously been around 40 ppm were in a free fall as well. My ammonia has remained around 2 ppm. I checked my pH and it had dropped to 6.0. I did a small water change, about 15 gallons, and reassessed everything later and the only thing that changed was my pH. I read that your pH can fluctuate through out the day so I checked it several times yesterday and it went from 6.4 to 7.2 back to 6.0 and was 7.6 again this morning. My ammonia is still at 2 ppm and my nitrates look to be between 5 and 10 ppm. Nitrites are 0. I have no ammonia in my tap water but I do have about 5 ppm nitrates in my tap. My tap water is also very alkaline at around 8.6 right out of the tap and it off gases to 7.4 after 24 hours. What is going on with my cycle? Why is my pH fluctuating so wildly? I have no decorations in the tank and I have a heater set to about 82 farenheit so the water is warm. I feel like I messed something up and I have no idea how to fix it.

 

[SaraB]

Are you planning on ever putting decorations in there? Beneficial bacteria lives on the surface of things so I always thought you put everything in before cycling. It also lives in your filter media so you might be ok.
Nitrates at 5-10 ppm are good, you don't want them 20+
Nitrites at 0 is perfect
Ammonia also has to be at 0 I think keeping up with water changes will help with this.


Sorry i have no idea what is happening with your PH This website might helphttps://www.firsttankguide.net/ph-troubleshooting.php