[laverda]

There are too many unknowns to know if 40 ppm is even a problem. If they are fish only with low light levels, it does not matter. If you going to have bubble tip anomonies they will do great at 40. There are plenty of corals that will even do well at those levels or higher. There are a lot of corals that will not tolerate levels half that. Also when you add enough light for anomonies and corals, algae is going to be a problem.
With out more specifics, I suspect the root of you problem is you backpack filters. While the do a great job of removing particulate mater from the water column, it is still in the system. All the crap you filter collects starters to brake down in to nitrates and phosphates. Unless you clean them at least weekly they are going to be nitrate factories. At this point I would suggest cleaning them twice a week to help get your nitrate levels under control.