What is the purpose of an overflow box?

[Henry100]

What is the purpose of an overflow box and is it necessary for every tank?

 

[eckrynock]

An overflow box is the way people who do not have drilled tanks get water from the aquarium to some sort of external filter, usually a sump below the tank. They are not necessary if you aren't planning on having an external filtration (skimmer in sump, refugium, etc.).

 

[STEELERFAN747]

The overflow creates a barrier between your display and the drain pipes which gives less oportunity for your fish getting trapped in the pipe and causing your tank to overflow.

It is not necessary in every tank as there are plenty of ways to drain the tank, however it is one of the more secure ways.

 

[hllywd]

The overflow box takes surface water from the tank and delivers it via drilled drains or a U tube drain to a sump where you may have your skimmer, refugium or other filtration devices. The over flow box also sets the water level in the tank by being raised or lowered. A return pump located in or plumbed to the sump pushes water back into the tank causing water to "overflow" into the overflow box and draining back to the sump in a continuous cycle.

The advantage is that the wastes a skimmer removes do not disolve in water and float on the surface blocking gas exchange. This is why most hang on skimmers at least have a surface collection option.

Tim

 

[oldsaltman]

It also allows for your siphon to restart if the main pump stops by holding water on both the inside and outside of the display tank. If you use a direct siphon it will not restart by it's self.

 

[jmait769]

Look at this from Melev's site on <a href="http://www.melevsreef.com/allmysumps.html" target="_blank">How a sump works</a> for a good explanation and visual example.

Jay

 

[Henry100]

Thanks for the explanations!I do not use any sump until now,thus I don't have any need for building an overflow box.But in the future,I may use one...

 

[dga]

an overflow also does not have to have any external vessel for containing water and can be completly intank. the nanocubes use a basic overflow (rear wall) i use one in my 20 gallon, houses a pump to skim the surface water, my heater, any carbon i may want to run, a foam pad to use after stirring up the tank during water changes, (cleans the visible junk much quicker), the grounding probe. all makes for a neater looking tank...