It's a separate test kit. I am using one by Red Sea. The testing process is a pain in the butt. The ppm is determined by the salinity and the temp of water. For freshwater, 8 ppm is good in the range of 72 -78. If your temp is below 72, the ppm should be 9. And ppm should be 7 if over 78.
The best way to increase o2 is by additional airpump or powerhead, lower temp, and decrease in fish. I use airpump on tanks that only have canisters, and no airpump for tanks with w/d.
Testing o2 is a waste of time because you must have adequate aeration to begin with, or your fish will die. I test mine because I have denitrators and need to monitor the bacteria level to make sure they don't consume too much oxygen.
