I was told to do 10g weekly water changes. I thought it was 10% water changes n I believe .10 x 40 = 4g.
Since I believe I have 40 g with rocks haven't done the math but I'm guesstimating lol
Automatic water change .
Changes water slowly throughout the day. There's a good thread on RC. I'll post it when I get home or just Google it.
Most have success with a Stenner pump, not dosing pump.
Just do a 5 gallon bucket every week. That is what I do on my tank (about 60g water volume). If your corals are exposed to air in the process I wouldn't worry about it too much since it will only be for a few minutes. Most coral will be fine I would just be careful with any sponge corals being exposed.