Most saltwater tank owners have a protein skimmer and choose to run the skimmer 24/7 because there are only a few situations where you should be limiting or suspending the use of your skimmer.  

  1. Not all aquariums need a protein skimmer, especially nano tanks. You simply need to do larger weekly water changes to remove the nutrients instead of relying on a skimmer.
  2. You should turn off your skimmer temporarily when using certain additives, medications, and coral foods. Amino acids, liquid coral foods, bacteria additives, and cyanobacteria remover all require that the skimmer be turned off for at least 30-60 minutes to ensure the particular additive/supplement is not immediately removed by the skimmer.
  3. The use of two-part epoxy directly in the display or failing to rinse a brand new filter sock before use will cause a skimmer to over-skim. Sometimes to the point at which the skimmer cup overflows. If this happens, turn off the skimmer for 24-48 hours, run some fresh activated carbon to remove the chemicals, then resume the skimmer operation thereafter. 
  4. Some hobbyists with low-nutrient aquariums choose to put their skimmers on a timer and only run them for so many hours per day. This is not very common and may potentially affect pH inside the aquarium. A better approach is to just increase the amount of food input or use nutrient additives in order to balance out the nutrient level while still running the skimmer 24/7.

To sum it up, running your protein skimmer pretty much all the time is your best approach to ensure your get the maximum benefit of nutrient export, gas exchange, and a stable pH at all times. You should only suspend your skimmer temporarily when absolutely necessary to avoid the removal of beneficial additives, food, and medications. If you find there are chemicals or something in the water that is causing your skimmer to overflow, do a water change and/or run carbon to remove those contaminants before resuming skimmer operation. 

If you find your tank is running with low or limited nutrients, it's much easier and safer to simply increase the food input or dose nutrient additives than it is to try and balance your protein skimmer on a timer. This will ensure you're not causing even more severe pH swings in the tank.

Learn More With BRStv: How To Master Your Protein Skimmer | Neptune Apex Controller Setup Guide