I had been having weird pH drops in my 5.5g tank for the past few months. It would be at 6.6 one day, and the next day below 6. I ended up changing the water more due to low pH than high ammonia/nitrites/nitrates.
Anyway, I did a little bit of research on how to correct low pH and a popular home remedy is to add about a tablespoon a baking soda for every 10 gallons. So I added about half a tablespoon and my pH jumped from less than 6 to about 8.2 in a matter of a minute.
To any extent it essentially nuked all of my BB. I have been getting solid ammonia readings now (no nitrites or nitrates) for the past couple days which, to me, indicates that my nitrogen cycle completed folded.
Any ideas how I can stabilize my pH again without using baking soda? I've read that crushed coral works pretty well.