Internal vs. External Overflow

[trothatl]

Newbie here with my first post... I've been lurking for a few weeks while reading and researching saltwater and reef tanks. I'm putting together an equipment list for my first tank (probably a 55-gallon tank), and I was wondering if anyone had advice/opinions regarding the use of internal vs. external (hang-on-the-back) overflows.
I haven't been able to find any information directly comparing the two. I did read somewhere that an internal overflow is "more efficient" than an external, but there was no explanation as to how efficiency was defined for an overflow.
From my own observations, it seems that an internal lets the tank be placed closer to the wall, is less noticeable, and doesn't have the problem of losing its siphon in a power outage, whereas the external's primary advantage would be that it doesn't require drilling of the tank but it takes up tank volume.
Are there any other considerations that I'm missing? Even it comes down to personal preferences, I am still interested in opinions.
Thanks!

 

[wanabebell]

Welcome to the boards
I dont know if there is really a difference besides the problems mentioned
except that if you buy a tank that is "Reef Ready" you wont need to worry about drilling it will come with an internal overflow
but i cant really help any more on this subject

 

[kalied20]

I setup a 90 gallon RR AGA with a 25 gallon Sump/refuge recently. I love the internal corner overflow. Everything in the tank and not a lot of equipment behind the tank and hard to get to. The tank was predrilled in the bottom 1''. I like this setup, but have to say that I haven't try the external. There are opinions on both out there.

 

[1knight164]

The only other consideration i could think of, although very minor, is that it takes up space in the tank and could be noticeable from the front. This would only be a problem if your goal is to keep as much equipment out of the display tank as possible. Otherwise, you seem to have the basis covered.

 

[1knight164]

Forgot to say WELCOME! Looking forward to seeing pics of your tank. I have a 55 as well.

 

[jmick]

I recently upgraded from a 55 with an external overflow to a 125 RR. I think the internal is more reliable, makes less noise and looks a lot better. The price difference between a reef ready and undrilled tank is comparable, especially when you throw in the cost of good overflow box. IMO, there is no reason not to buy a reef ready set up.

 

[redlinedcj]

i have an external and i am right at the limit of flow for the U tube i guess i can add another but thats kind of a pain i think internal would be able to support more GPH then external

 

[trothatl]

Originally Posted by redlinedCJ
i have an external and i am right at the limit of flow for the U tube i guess i can add another but thats kind of a pain i think internal would be able to support more GPH then external
That's an issue that I hadn't considered -- I agree that the internal overflow could probably handle a greater flow rate than the external. And the noise factor that jmick pointed out could also be important.
I probably will end up with a reef-ready predrilled tank, but my tank options are much wider if I get a non-drilled tank and use an external. Then again, it looks like the cost of a good overflow box cancels out potential savings from buying a non-drilled tank.