Pros/Cons of external (builtin) overflow
 

I'm trying to decide on whether to spec out a tank with an external overflow box as opposed to the more traditional internal box.

This is how I see it so far:

pro: you retain the all the original tank volume as usable for aquascaping. May be more aesthetic.

con: The glass needs to be notched out, potentially weakening it. Also you have only one water overflow edge, as opposed to three edges, thus the potential for blockage is increased.

Another con is that it complicates how to move the tank (unless the box is retrofitted after the tank is in place).

I had originally wanted to go with the external, but the tank builder has almost talked me out of it .... can someone talk me into it?

how about doing a coast to coast overflow? they look very clean and dont have the "bumps" you see in a more traditional setup. plus you dont have to have the tank sticking so far out from the wall.

I got the external on the 67g, I just love it. I wish I had gone that route with the 230g.

I know Jim Barry is getting the externals on his tank that IA is building.

Doug doesn't sound so keen on them... How hard did Jim have to lobby for them?

I might have to get them installed afterwards seeing as they could seriously complicate getting the tank downstairs and around a bend.

The coast to coast overflow sounds neat too, I had thought about that but forgot to mention it to IA as a possibility as well. Thanks for reminding me Willow, I'll check into that as well.

Hey Tony,
Well I had some of the same concerns when setting up my reef as well.
This is what I ended up doing, I purchased a piece of black plexi($5) from a local plasic store and asked them if they you cut some overflow teeth in the top, I also had them bevel the edges for an additional $10. I knew by this point that I would simply cut off the back right corner of the tank at a 90 degree angle. This gave me a triangular overflow box of 6" per side.
It works great, and best of all it took up a minimal amount of space in the tank.

Hey Tony,

I have put a fair bit of thought into them for my new tank aswell, all said and done, i went to external.

The reasons for this were, Aesthetics...a big one.
-It can be a much bigger overflow externally with more overflow capability without the eyesore.
-no blocked lighting into the tank...and less algea in them, though that is an assumption on my part...havent quite got water in it yet.
-Increasing usable tank space is always a bonus, aswell as added volume.

Not sure if this is an option for you, but for mine i wasnt worried about weakening the tank`s back wall, if you decide on a "tank length" overflow (just the bottom of the box will work aswell.).... the bottom of the overflow will become a perimeter brace.

Marc.

Tony,

When I was talking to Doug at IA, his main concern was putting the overflow in the middle of the back of the tank. His concern was that it could ruin the stability and cause the tank to bow out and potentially break.

Why couldn't you put the external overflow on the back closer to the end of the tank. This may give it more support instead of placing it in the middle, at the back.

His concern with the potential of blockage of the overflow is a concern, however if you made the opening wide enough I don't think it would be a problem.

When I ordered my tank, I met with mitch, who recommended I go with external overflows. I am putting one overflow on each end, so blockage or glass stability shouldn't be a problem.

HTH

Jim

Marc, are you going with a full length overflow? Do you have any pictures? What length of tank are you going with?

Jim, thanks for the advice. Yeah, I had originally (in my haste of drawing up some rough sketches) put the overflow in the centre of the rear panel, thinking "I will sort this out in more detail later." So putting two overflows nearer the sides maybe would work better. Do you have any pictures of your tank?

Thanks for the advice everyone!

reply
 

Hey Tony, have you totally ruled out drilling? Why?

My tank has a overflow box built on the inside of tank. If I would do it again it would be an external overflow. Here is a few of my reasons.

- Blocks some of the light for the corals. Thus I can't put corals underneath it.
- Takes up more space in the tank than I really like.
- External overflows always look cleaner and neater while viewing the tank.

EDIT: Actually more or less the same reasons as Marc.