Edwin has said it....this is just the initial dose to adjust from 400 to 420....which is easiest to do manually. I personally have no problem with 400. But if you do want to adjust up to 420, I'd suggest dosing half that volume, and then testing. I've found these calculators to be funky....maybe because we don't do a good job in guessing our total tank volume. Once you've add this first "half," adjust the second dose accordingly.
Again, as Edwin stated, you then need to determine your daily consumption. I did this by picking a number (for your tank, I would start out dosing 200 mls per day). Then I'd test daily to see if I needed to adjust the volume up or down.
I too have BRS pumps (1.1 mls per minute), which I control with a Reefkeeper. If you have a controller that controls to the second, you might wish to consider the 50 ml per minute pumps they sell, since you're dosing bookoo amounts.
Again, as Edwin stated, you then need to determine your daily consumption. I did this by picking a number (for your tank, I would start out dosing 200 mls per day). Then I'd test daily to see if I needed to adjust the volume up or down.
I too have BRS pumps (1.1 mls per minute), which I control with a Reefkeeper. If you have a controller that controls to the second, you might wish to consider the 50 ml per minute pumps they sell, since you're dosing bookoo amounts.
