Nice looking tank. I too had a fluval, I started fish only then moved to reef. Do you test for nitrates? I removed my fluval about 3 months ago and it seems to have reduced nitrate levels, although they were not too out of wack with it (10-15ppm, now less than 10ppm). Nice corraline growth on the back glass.
What is your alk, you say it is lower than should be. Also, what test kits do you use...hopefully not RedSea, could give faulty readings. Based on your corraline growth and "look" of corals I'd guess your alk is fine.