I use an the same filter on my 46 and I also use a magnum 350. In the aquaclear I use the foam insert only and 2 units of Chemi-Pure on top of that. In the magnum I only use a foam insert.
I have zero nitrates and have not had any nitrates for over 6 weeks now. (Actually it is the first time I have ever had zero nitrates)
But it takes some real discipline. I do weekly water changes of 8 gallons and I change out the filters in each unit. The foam insert in the Aquaclear you can clean and re-use. I have 2 filters and I just rotate them in and out. The magnum 350 I use a new one each week.
I also use the remora aqua c protien skimmer but I am not entirely happy with it's performance.
I guess I am beating the odds. I agree that crushed coral is a trap for waste but I guess I am doing a good job of keeping the tank clean and not overfeeding. When I first started the tank I converted it from fresh water with a reverse flow UGF. I took the UGF out but I left the crused coral in. I started out with about 15 nitrates and it slowly went down. Lots of water changes and taking care not to overfeed. Only 4 fish and no corals.
So whatever you can make work for you will work.
Good luck,
Regards,
Pat