overflow, so many decisions....

[Delphinus]

I think some of the considerations will depend on what you want.

In some situations, you have a tank and stand, in a standalone situation. In this scenario you may prefer to have the bottom drilled so to minimize the plumbing outside of the stand.

However this at the cost of real estate in the tank.

A hang on the back overflow eliminates any space being used up in the tank, however with only one edge for the waterflow, can perhaps be prone to clogging more easily than say an internal overflow with three edges. However I don't think that's the hugest of concerns.

If you want to be really technical, then you should consider something along the lines of a "coast to coast" overflow. Feed your skimmer with raw overflowed water, the maximized overflow edge means maximized protein extraction (since proteins will float as a "surface skum").

To be honest though I wouldn't really sweat it too much. Make sure your overflow is sized for the flow you want it to handle, and have some fun. I've tried many different overflow styles and to be honest they're all the same in the end.. if they get the job done that's the most important.

However if I was to build a new tank from scratch at this point, I would be going coast-to-coast on the overflow. I let myself get talked into an "old school" corner overflow for my 280g by the builder... I do regret this a little bit, but I'm not changing it now, I'm not hauling that tank out my basement for that!! In the end it was little cheaper so I guess it wasn't a huge loss.