Fuge will increase O2 when lit, that H380 puts off worlds more light than the H80, so heat will be a factor also. Only slightly since its LED, but I had a H380, you can feel it. A bigger skimmer will also increase temperature and O2 but could also increase CO2. Its increasing gas exchange and if your house is tightly sealed you could introduce more CO2 to the tank by increasing the gas exchange with the skimmer. In that case, maybe a CO2 scrubber on the skimmer air inlet. pH should skyrocket after that.