Tell us what your ammonia, nitrites and nitrates test readings are. Next what is your salinity or salt level? You use fresh RO/DI water to replace evaporation, in my case my 16G nano takes about 2-3 gallons a week depending on the humidity and how I have my powerheads aimed for surface agitation. You use new saltwater to replace what the skimmer removes since it removes the salt too. You use new saltwater to do regular water changes, 10 to 20% every week to two weeks. Keep an eye on your salinity since it will drop with wet skimming so you may need to add a small amount of salt when replacing for evaporation or you can account for that when you do water changes. Sounds like you may still be in the midst of a cycle though and water changes may prolong the cycle, posting your test results will prove this out though.