You can, for small changes on a small tank. You want to make sure that the 2 Chanel’s are dosing the same as each other. Even then I would keep an eye on your salinity. Most dosing pumps are designed for very small volumes. Dosing pumps fail over time as the hose becomes elongated and no longer function as original. This will happen faster the more you use them. Also the rollers wear and the motors fail. For these reasons they do not work well for larger tanks.
I have never been able to get this to work over a long period. You just cannot accurately match the output and input and eventually you have an imbalance. Sure you can calibrate all the time however there are easier ways.
Like Slawman said, hobby grade dosing pumps are not quite accurate enough and the in/out will not match. This can lead to issues with ATO/salinity and even flooding. If one of the heads were to fail and the other kept going that would be a huge problem. People make it work but it just puts too much reliance on equipment IMO.