I noticed the Ph is climbing a little, it's at 8 right now. Would a water change help bring this back down, or will it gradually come back down a little?
In regards to the PH, keep monitoring it. If it stays the same roughly, don't worry about it. Fish can tolerate a slightly higher PH with much less trauma than happens if you're constantly trying to alter it with chemicals. You'll need to pay slightly more attention to the PH requirements of each type of fish you desire, but 8 is low enough that it should be ok with most fish and it's low enough that fish who are just outside of that range can probably adjust and live.
If you absolutely must lower the PH, do a few water changes with distilled water, or add some peat moss to your filter (disclaimer: I have not personally tried the peat moss method, i've simply heard good things).
Peat moss can turn your water a slight brown colour which is desirable in some set-ups but in this one I don't think so. Slate can also raise pH so you may want to get different rocks.