Gemsurfs also have those single channel marine magic 1+1 doser. And if budget not an issue, saw on freshnmarine website that they have those grotech single channel doser too.
http://www.gemsurfs.com/mm01b.html
http://freshnmarine.com.sg/estore/smartphn/product_info.php?products_id=100&osCsid=61b670590222e0791d3c7349bd5acabf
Cheers
Perhaps u can spread out your rocks out instead stacking them all to one corner. It will give your scape better flow and better distribution to allow u to place your corals in future. My 2 cents.