The friendliest place on the web for anyone with an interest in aquariums or fish keeping!
If you have answers, please help by responding to the unanswered posts.
IMO the Cabomba will just shed and melt away at that low light. If you want a fine leaf background plant that look almost the same but doesn't need as much light, look at Giant Ambulia (Limnophilia sassiliflora). Even with it 15w is really low light. Good luck. OS.