Thoughts on Internal/External Calfo Overflow

captbunzo

captbunzo

Premium Member
I am (still) working on the setup of a 90G reef tank for my older sister. To this point, I was planning on installing an internal Calfo overflow at the top, back edge of the tank. It was going to be about 4x6, and run most of the length of the back of the tank. The larger cross section is required do to the need to install fittings in bulkheads to stop creatures from getting suctioned down, etc.

However, I have been really bothered by the overall size of this beast. It just really takes up a huge amount of space in the top/back of the tank. Also, it seems that it is going to block just way too much light in the back of the tank.

So, I had an idea recently. What if I trimmed that internal overflow down to not more then about 2 inches in depth (front to back). And then installed a larger overflow "drain box" behind the tank, allowing the water to flow through several holes drilled in the back glass of the tank, in between the internal horizontal overflow and the external drain box.

My thought is that this would be a great way to keep the benefits of the horizontal overflow in such away that also didn't take too much internal room up inside the tank.

Also, the back drain box could be split, for convenience, if I like.

So, any big drawbacks I haven't thought about? I think this would still accomplish the goals of a horizontal (Calfo) overflow. Does anyone disagree on that point?

I will try to post a diagram soon.
 
The idea is fine to me internally... as long as you can block all macroorganisms thoroughly from entering it (and with the understanding that if anything (snail... whatever) does bypass your guard... it may be VERY difficult to extricate.

But as far as having the larger external trough at the same time... I see no need or advantage. Just drill the back wall of the aquarium up high through which the internal overflow water... er, flows.

But a better solution IMO for you in this case... may be to have the rear wall of the aquarium cut/ground down (or if new/custom... they will glue a short wall) so that the rear wall of the aqurium overflows into a/the larger rear trough that you are already willing to have (and this avoid any internal box that you are clearly reticent to have). This is best in your case to me.
 
Ah - sorry to not mention. The 90G tank involved has already been aquired. It is a standard tank and I don't REALLY want to go as far as cutting/grinding down the back edge of the aquarium.

As for not needing the trough, perhaps (and probably) I am confused. I am coming from the mindset of "deeper" overflows which benefit from some sort of fancy standpipe to reduce the noise of water overflowing, draining down the pipes, etc. Your thoughts?

And, btw, just for kicks and grins, I did make some diagrams, which was fun in and of itself. :)

splitoverflow-front.jpg

splitoverflow-top.jpg

splitoverflow-side.jpg


If the noise isn't so bad, then perhaps the external boxes are completely unnecessary... :)
 
you could take the top trim off the tank and extend the glass with a collar on three sides. Then dress the top of the tank again.
 
I think for now I am going to try a 1-2" internal box draining right out and down. I'll get it all sawn, glued, drilled, and filled and see how noisy it all is. If it's a problem, then I can always go back at that point and add the external boxes/standpipes.
 
I am debating this same issue as Paul, as it relates to how wide front to back the internal overflow will be in the tank. I want it wide enough that I can remove the 1 1/2" elbow that is connected to the bulkhead if I need to but not so wide that I am blocking light to the back of the tank.

I have two 1 1/2" bulkhead holes drilled in the upper right corner of the tank. I am planning on having the internal acrylic overflow trough made so I can glue it to the top back wall of the tank. Do I need the elbows or can I just use strainers sticking out of the bulkheads? I assume the elbows are to help reduce the water noise. I am planning on putting a "tee" on the back drain hole to create the durso standpipe (I think that is what it is called). So is it necessary to have the elbows inside the tank? Ideally, I would like to have the trough only 4.5" (the .5" is for the ledge for star polyps to grow on the outside of the trough :). What are most people doing about this inside the Internal CALFO Horizontal Oveflow?
 
The elbow would make the durso concept more likely to work. I am about a week from setting this up. At this point in time, I am not planning on any sort of internal strainer or elbow, due to space limitations. Now, I may end up gluing some eggcrate to the inside of the bulkhead in an attempt to blow anything extra large from going down the drain.

With a 4.5" internal trough, though, you have quite a bit more room. I am aiming at around 2 inches or so. just enough room (basically) for me to get my hand, a net, etc, in to fish things out.

I'll report again when I have finally accomplished something. At least all of the parts have arrived in the mail! :)
 
What if you left off the internal part and just drilled some holes and then built the box on the back of the tank? Wouldn't that work also? As for the holes you could use any number of them and have some type of screening material to prevent occupants of the tank from having access.
 
<a href=showthread.php?s=&postid=6065566#post6065566 target=_blank>Originally posted</a> by Anthony Calfo
you could take the top trim off the tank and extend the glass with a collar on three sides. Then dress the top of the tank again.
Click to expand...
Anthony, I've spent hours looking for someone that has done something like this but can't find anything. I was considering doing an external horizontal overflow on a 180G AGA but it might be a little too much trouble to go through. If so, I will probably end up doing an internal horizontal. What do you think?
 
cheers, bleedingthought

I'm inclined to agree with you. If you are not familiar with (or have someone local) aquarium-making, it can be a challenge for you. That said, one with experience or just handy would have no trouble pushing a blade under the plastic trim to pop it off... then a quick scrape of residual silicone and light (super fine) sanding... then a clamp and glue of pre-cut glass strips. Literally... a one hour job. I wish I could remember the chap that came to me some years ago wanting to market this as a ready made collar for folks that wanted an external horizontal overflow. His prototypes were quite novel! Hmmm... I'm sure I saw someone post pics of an acrylic version here on RC a couple years ago too. Maybe it was a few years. Its an interesting though, but acrylic and glass aren't meant to be bonded. Truly... and as such, long-term I/we cannot expect it to not leak.

In your case, here, my friend... the tank is so wonderfully large that I think you can afford the easy/traditional internal horizontal overflow. Make it wide enough simply to get your fist in there for rescue (fish/snail) if your guard (gutter-guard, for example) fails. About 4" wide and about as tall (maybe a bit taller... to 6") would do the trick. Then run it as long as you like/can.
 
<a href=showthread.php?s=&postid=9296758#post9296758 target=_blank>Originally posted</a> by Anthony Calfo
cheers, bleedingthought

I'm inclined to agree with you. If you are not familiar with (or have someone local) aquarium-making, it can be a challenge for you. That said, one with experience or just handy would have no trouble pushing a blade under the plastic trim to pop it off... then a quick scrape of residual silicone and light (super fine) sanding... then a clamp and glue of pre-cut glass strips. Literally... a one hour job. I wish I could remember the chap that came to me some years ago wanting to market this as a ready made collar for folks that wanted an external horizontal overflow. His prototypes were quite novel! Hmmm... I'm sure I saw someone post pics of an acrylic version here on RC a couple years ago too. Maybe it was a few years. Its an interesting though, but acrylic and glass aren't meant to be bonded. Truly... and as such, long-term I/we cannot expect it to not leak.

In your case, here, my friend... the tank is so wonderfully large that I think you can afford the easy/traditional internal horizontal overflow. Make it wide enough simply to get your fist in there for rescue (fish/snail) if your guard (gutter-guard, for example) fails. About 4" wide and about as tall (maybe a bit taller... to 6") would do the trick. Then run it as long as you like/can.
Click to expand...
Anthony, thank you for the response! That was my initial thought about the external overflow. I was going to use a dremel and "file" down about 1/2" in the back under the trim. I have never done such thing (use a dremel on glass), though, and I've got to admit that undergoing such a task on a brand new tank, my biggest thus far, is quite intimidating. :) You do give me a little more confidence about it, though. I would definitely use glass, probably just 1/4", and have holes on the bottom of the overflow for the drains and returns. One thing that scared me was that I read here on RC about a guy that did it to his 75G tank and it cracked the next day, from one of the bottom corners to one of the corners he filed to, while he doing a water test. :eek2:

Well, if I were to do the external, what other pointers/encouraging suggestions do you have for me? :) And if I were to go with an internal (definitely less scary!) how long would you go? I was thinking 4 feet as that would probably be the easiest size to get. But that's just me, thinking...

Thank you!

Thiago
 
And oh, what about tank braces? How am I to go about dealing with them when doing an external overflow? I believe the 180G (6 foot tank) has two of them. :confused:
 
i had mine built with a full length external overflow, rear glass panel about 1/4" lower than the rest (no teeth or screening) and about 6" x 6" internal dimensions. the extra width is nice for floating bags and sticking frags and rocks in while re-scaping, and if you want dursos you'll need the depth. and my plumbing takes up that space behind the tank anyways.

it's eurobraced on the front and sides.
 
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