Even if we know how many gallons is our tanks like mine 12g we cant say how much water is in it cause of the LR AND LS??? so is there any formula for that doubt it... personally i think my 12g nano has only like 8 gallons of water or less ...TimSchmidt said:Just remember to take into consideration that you should measure the INSIDE of the tank, otherwise you will get a number that is a couple gallons off. Not too serious but if you are medicating a tank you will definitely want to know how much water is really in your tank, not how much glass and water you have in your tank. JMO
Tim Schmidt