Extra dry chamber next to intank overflow - what is it? pic attached

[Raysocal]

I bought this tank used and the orginal owner is not availble. I attached a photo of the top of the tank overflow and as you can see there is a narrow dry chamber connected to the overflow that extends the entire height of the tank and there is no opening at all except for this one at the top. Does anyone know what it could be for? I thought maybe he had it made to store cleaning tools or could it help dappen sound from the overflow? Thanks

 

[frickr]

its for running wires, equipment hoses, or whatever else you can/want to get through there, so you dont have all the ugly stuff hanging off the back of your tank. put a nice hood ontop and you wont have anything showing on the back of your tank.

 

[Raysocal]

It's not open anywhere else except the very top. If I want to run wires then I drill a hole in the side towards the bottom of it and thread whatever line through the hole? Thanks