From what i've read so far, while cycling doing water changes help out. These shouldn't be major water changes, but something along the line of 10-20% every week.
If you think about it, ammonia, nitrates, nitrites, etc, will remain in the water, by doing water changes, you're removing these components out of it and bringing in fresh water which will help remove these from the tank and should help stabilize things further.
Ph changing so much can be just part of the cycle itself. There are several components that help buffer the PH in order to maintain a stable system that takes a while to develop. So even though, one day you'll measure a good PH value, a few days later things will be different.
I haven't tried adding ammonia to my tank, and I probably won't. The LR that I picked up was fairly developed and had been in tanks for a really long time, so I figured it would be counter intuitive to artificially raise the ammonia levels, and I'm letting things go in a more natural route.
I also would think that adding ammonia, it's something that you would do at the beginning but not continuously add more. Basically, the concept is to put some in there to help the nitrifying bacteria to start doing their job, which will start the whole nitrite-nitrate cycle.
From what I've read as well, you don't want to use huge amounts of ammonia, and a good way to go about it, is to just drop a dead shrimp or something ( from a supermarket ) which will help release natural ammonia and help out the bacteria do their job.
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