over flow tanks

[casey]

whats the deal with these? why do people use them? Do u need one for a 75 gal? Can some one explaain this to me?

 

[mr . salty]

OVERFLOW TANKS??????????????This means nothing...Are you refering to tanks with built in overflows,,,Or overflow boxes for tanks without built in overflows????In either case an OVERFLOW is just a way to get water out of the main tank and into a sump.The "sump" is a tank that usually sits under the main tank and can house a number of things including filteration,skimmer,refugium,dosing equiptment,and so on...A sump also increases your total # of gallons in the setup.