Sorry, gotta jump in. I t hink that 2 pumps for this is a bad idea. You just create more points of failure and more heat. Rather, do this:
1. tank drains into the fuge
2. fuge drains into the sump
3. sump pumps back to the tank
You need very little height difference to let water flow from the tank to the fuge. And flow rates can be identical for each. Just use a Mag 7 for the return pump from the sump to the tank.
As for "slower flow rates in a fuge", that is nothing but mythinformation. Not really necessary. Search for "mythinformation" on this page to hear more details on that from Anthony Calfo:
http://reefcentral.com/forums/showt...age=25&highlight=mythinformation&pagenumber=2
And don't mess with some unknown pump from Home Depot. You won't really save much (if any) money and will cause yourself far more hassle. Go with a Mag Drive as they are tried and true low cost pumps. If you want to spend more for something better, I am sure folks can recommend as well. (Iwaki, for instance)
As for the calc reactor idea, I think that is a neat one. Sounds like a good way to keep pH stable and reduce one of the risks of running a calc reactor.
Honestly, I would recommend that you skip the calcium reactor and invest in an auto-topoff system and use kalkwasser. Contemplate calc reactors if the simple solution (Kalkwasser and auto-topoff (which is great, anyhow)) doesn't work for you.
Just my two cents or so...