The salinity, Calcium/Alklinity, trace elements, and pH swings are the primary concern of these little nanotanks especially when you are doing tons of ro/di water topoffs. I would say that the main difference between a salt and freshwater nano is that the salt nanotank would require weekly water changes. I don't believe freshwater nanos require such maintenance. Yes, actinic lighting provides for coralline growth on the live rock. The coralife mini aqualights would be perfect for this application. Hope this helps!