The ghl is a really good doser. I have been running one for about 6 months and really like it. I would recommend it to anyone. My only criticism would be that the initial set up can only be done on a pc. I had to borrow my gf's because all I have is a Mac. Now I run it through the iOS app on my iPad. I've been thinking about going with the Neptune doser so I can control everything in one place through fusion. If anyone has any interest in buying this one let me know, I'll sell it for $300.00. It is this model
http://www.aquacave.com/ghl-profilux-doser-2-4-pumps-with-wi-fi-controller-black.html with 3 heads and the slot for a 4th. I still have the original box and manuals plus all the downloaded set up instructions. All of the people at GHL are really helpful, Artur has helped me a few times by remote access.