Bottom drilled vs back or corner overflow?

kyley · Feb 23, 2019

Hi all,
I'm looking for a new 75 to 120 gallon aquarium, and I see all sorts of different drainage types. Is it preferable to have the bottom drilled, an overflow box on the back or corner (drilled on the back wall), or something else? And why? Only consideration I could think of is that having the bottom drilled could be a catastrophic loss - compared to a leak if it's drilled at the top for an overflow box?

Background: I've been running a Red Sea Max 250 (65g) all in one for about 10 years now, so I'm new to running a tank with a separate sump. Thanks,
--Kyle

Billldg · Feb 23, 2019

There r plus's and minus to both, I picked a tank with the overflows in the back because I didn't want to see the overflows from the side, but you lose a little space along the back wall to accommodate the overflows and the opposite goes for corner flows, you have a little more room along the back wall, but you have to look at the overflows from the side. It comes down to what your want you want really. I have a 120 gal tank with dual overflows in the back wall. IMO, I think the best tanks are really the ones that r drilled on the back wall and the overflow boxes hang on the backside of the tanks, best of both worlds. They do cost more though.

malacoda · Feb 23, 2019

It all boils down to choice really. Each of slight pros and slight cons but in the overall big picture one isn't really 'better' than the other. It's more a matter of which fits your desires and/or space better.

In most cases back over flows mean less real estate being taken up inside the DT. And they often give you the flexibility of setting up a 3-pipe Bean Animal set-up which runs silent and almost completely eliminates the possibility of an overflow overflowing due to a blocked drain pipe.

The con is they protrude from the back meaning your tank will stick out further from the wall taking up more space in the room. And if a drain pipe bulkhead leaks it'll go straight to your floor versus inside the cabinet. Of course, you could always get a deeper stand and cut a hole in the top so that the pipes run down into the stand and any leaks would drip/run down into the stand as well.

An internal overflow will use up more space inside the DT. Unless it's custom, they usually only have two holes, sometimes three -- one drain, one return ... or two drain, one return -- so you will either have a somewhat loud/gurgling drain pipe or a herbie-style drain that is quiet but still does have the slight possibility of being clogged (pretty unlikely but can happen with, say, a rogue snail, etc.). The pro is that you can set your tank closer to the wall and take up less space in the room.