User blog comment:Rassilon of Old/Young Justice spoilers at Comic-Con 2012/@comment-112.202.0.227-20120804141452/@comment-4821105-20120804224545

Atlanteans can also use "normal sorcery" like Zatanna but Atlanteans magic isnt about water. Both Tempest and Aqualad can use electric powers due Atlantean magic.

Garth/Tempest was on team at same time as Tula/Aquagirl did, but he left when Tula sacrefice her life to the team continue their misson. Or He is training or helping the team looking for some help since Black Manta is working for The Light and Ocean Master was working for The Light as well. Aqualad probably doesnt talk too much about him since Garth is the guy that stole Tula from him.