On my 125 I run 2x400 20k XM's and my sps love it. I have run iwasakis in the past, but after these 20k's ill never go back. The color is amazing and growth hasnt slowed a bit.
I wouldnt suggest either for a 46, unless you buy them when they are small and upgrade as they grow. I would consider the tang rule for them- min. of 75. They dont cruise around as much as tangs but they are more delicate. I believe the auriga get s about 7-8 max but in aquarium im estimating...
My tang had this once back in my FO days. Do they look like small red veins? I can not remember the disease name, but do remember I used maracyn 2 to treat it.
Check the for sale or trading forums here. You could build a simple DIY venturi its just a tube with a collection cup.... im not sure but i think Aqua medic sells the replacment needlewheels for there pumps, or maybe euro reef, you could buy on of those and put it on a rio and make a good...
I have borrowed that book from a friend and read it, but first I need to get my clowns to spawn! Sounds like a rewarding project, I will have to give it a shot sometime.
Clwn
I would say beckets are the best, then downdrafts and needlewheels. I would make a venturi, they are probably the easiest without making them huge. I would just look for used skimmers my self, like a bac pac or remora.
I do what BB said and also run some carbon just incase you colt is unleashing some chemical warfare with your zoanthids, From what you said i doubt it is,but just in case I would.