Depends on your budget mate
Cheap ones which will do the job are - Jebao
Midrange-kamoer, bubble Magnus aquamedic, TMC
If money is no limit- GHL, Apex Dos, Kore
I use GHL for my reef (i run an aquarium controller for both my tanks) and Jebao for my planted. I did use Kamoer, very good unit but altering doses can be a pain, the Wi-Fi version is hit and miss
Sent from my SM-N950F using Tapatalk