What would the largest main by if the sump held 60 Gal?

[KurtsReef]

My scheming mind has been at work, if I were to convert my 75Gal into a sump/ref what would the largest main I could have be? I would use a figure like 60 gallons to be on the safe side.

Is there a formula for this? I "Just did it" when making a sump for the 75 gallon and gave it no real investigation or study.

[tecwzrd]

IMO a sump should be at least 25% of the mains total gal to be effective.

i.e. a 75 gal tank should have a 18.75+ gal sump so a 75 should be able to accommodate a tank up to around 220 gal or less.

Of course the bigger the sump the better but having at least 25% of the mains total typically will give you enough room for equipment and baffles and is able to handle the overflows max volume of water.

You will probably only get about 50-55 gals of water usage out of the 75 using it as a sump with it 2/3rds full during operation to allow for drainage back from the main.