That made my decision to change the entire water quite easy, so out it went. This allowed me to clean out all the small particles that were in the fish tank as well. After refilling it and running a few flood and drain cycles, the water remains much clearer than before, and the PH is in the 6.5-7.0 range. Not exactly where I want it, but much better than before.
Next, I'll be off to a local Tilapia grower for some starter fish!