CO2 Scrubber - adding water

[hers0109]

I recently purchased a co2 scrubber for my tank and have it up and running. I added the 1-2 tbsps like recommended from the vendor. Question is… the water evaps after a day or two. Should I keep refilling with RODI or is one time sufficient until I change media?

 

[56longroof]

Just upon initial fill up.