Without a par meter to know for sure how much light the LTA is getting it's a guess. But if I may, it seems like you're moving up in the hobby in the sense of the livestock you're keeping. The Fluval is a good light if you're keeping fish only or fowler, maybe some basic corals. Instead of supplementing it with another light source maybe look into upgrading the light equipment. External factors may be preventing this but in the long run this is the way to go.