If you are talking about hooking up an oxygen tank to an airstone to add to the water then yes. If you over saturate the water with O2 then you can hurt your animals gills. If you are talking about adding an airstone then you will probably be okay, but you should test with a sample of your water (500mL or something) and run the airstone in the water sample for about 20-30 mins full blast, check your pH after that and see if the reduced CO2 levels have raised the pH more than you'd like.