water volume

I'm on the fence on whether to move my clownfish pair to a different future tank... Maroon/Percula. The tank is a 12x12x12 with an external overflow. While the DT is small. The actual water volume will be roughly 15-17 gallons when including sump. Thoughts? I think it will be fine. But wanted...

I've always wondered what manufactures really mean when they give dosing instructions based on "gallons." For example, Korallen-Zucht and Red Sea give dosing instructions for their additives in terms of X ml or X drops per 25 gallons. Gallons of what? Is it based on the rated tank size (my...