So, I have a 38 gallon aquarium that is overstocked, and I have spent the past couple months building a 330 gallon small outdoor pond/water garden to move most of the fish into. 2-3 weeks ago I knew I was going to have a problem because the pond is holding steady at a ph of 8.1, and my aquarium had had a consistent Ph of 6.9-7.0 for over a year. I freely admit maintenance was not frequent enough last year as I was dealing with a chronic illness flareup, but fortunately, no one in the tank seems worse for wear, including my bamboo shrimp. So I assume that was part of how my Ph ended up so far off of my tap water.
So the past few weeks I have begun aggressively cleaning (as much as I can without messing up the beneficial bacteria) and increasing water changes. After a 50% tank change earlier this week and then another 30% change today, my aquarium Ph just will not budge above 7.6. I also tried experimentally lowering the ph of some of the pond water in a bucket with ph down just to see what would happen, but within 24 hours it returned to 8.1ish after dipping right after application. Tap water is 8.1 out of the tap and according to the city water quality reports it ranges from 8.1-8.4, though I've never gotten a tap water reading higher than 8.1. The rest of the tank parameters are as follows after today's water change:
A:0 Ni:0 Nitrate:5 Kh
:12 Ph: 7.6 on API freshwater master test kit plus add-ons
Obviously, I can't safely move the fish with the ph off by .5, so looking for advice on a way to safely raise the ph by about .1 per day or so. I'm guessing it's time to pull out the baking soda? How often would you think I'll need to test the water to make sure it maintains a steady upward trend? Thanks for any advice.