I use a pair of drews dosers. Cheap and easy. They dose 1.5ml per minute and were easy to mount and problem free. I got mine used for 80 for a pair. I think new they are 75 or 80 each.
I am running the BRS dosing pumps.. they are very nicely made and reliable.. they dose exactly 1.25 ml a min. They are very accurate since i have spot checked the dosing a few times