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Old 06/25/2008, 08:44 AM   #1
cpeisher
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Overflow - Teeth or Not

I've seen several designs for overflows that don't have teeth. I always thought this was a no-no because of the risk of snails etc. getting into the overflow box and clogging things (or dying)? Is there a name for the straight edge overflow? I know that it is better in terms of skimming, but i would think that the risk of loosing livestock in the overflow would outweigh the advantages...


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Old 06/25/2008, 09:12 AM   #2
Patrick12
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Teeth all the way. They help in other ways too.....with the surface skimming. The snails can climb out of the water and will to get into the overflow....unless you have a top and teeth.


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Old 06/25/2008, 09:22 AM   #3
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i dont have teeth on my overflow, and yes i have had a couple fish and a roving RBTA get stuck in mine in a 2 year period. IMO toothless is quieter and was much easier for me to do. nothing has got stuck in my plumbing, i have stockman drains with several 1/2" holes in it. theres really not much chance of a plug from anything. i have the plumbing friction fit in the overflow so when i need to all i do is pop out the drains, which lowers the water level in the overflow and then i go fishing. works every time with no losses.





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Old 06/25/2008, 09:32 AM   #4
cpeisher
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will cutting teeth on the street elbows for stockman drains prevent snails from getting in the pipes themselves? Or is that really a moot point since fish can still jump over it? Would it be possible to put some kind of egg crate on top of the straight overflow edge to block out fish and snails, but still get laminar flow across the overflow?


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Old 06/25/2008, 09:35 AM   #5
GIJOE007
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IMO, teeth all the way, then what i did was cut some eggcrate to put over top (the egg crate fits right into the teeth slots so I have a flush top overflow)...I have no worries about tanything getting in my overflow


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Old 06/25/2008, 10:22 AM   #6
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I disagree. Teeth don't add anything (snails can climb over teeth just as easily at a flat weir), and have several drawbacks (reduce flow, reduce surface skimming, increased surface area for algae to grow on, difficult to clean, ugly).


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Old 06/25/2008, 11:33 AM   #7
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Teeth all the way. They help in other ways too.....with the surface skimming. The snails can climb out of the water and will to get into the overflow....unless you have a top and teeth.
I hate to sound argumentative, but these statements are simply incorrect - surface skimming is made more inefficient by teeth (we want to skim the surface, not 1/2 inch into the w/c) and snails [b]will[b] climb right over teeth. A properly designed overflow will have only a very thin sheet of water flowing over it which will prevent fish from being swept in. Do a search for Anthony Calfo's posts on overflows and you will find some good discussion on the vast advantage of a smooth coast-to-coast overflow.

This is not to say that many people prefer "toothed" overflows and have great success with their system.


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Old 06/25/2008, 11:58 AM   #8
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I would go no teeth, you can always clip on some gutter guard later.


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Old 06/25/2008, 12:08 PM   #9
BeanAnimal
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Quote:
Originally posted by Patrick12
Teeth all the way. They help in other ways too.....with the surface skimming.
Actually the opposite is true. Teeth impede surface skimming.

Lets take a 20" long FLAT overflow... it has 20" of surface skimming area.

Now put 1/4" wide teeth with a 1/4" gap in that overflow. You now only have 10" of open space... or 10" of area available to surface skim. Given the same volume of flow from the return pump, the water will be twice as thick over the toothed overflow. That means less surface turnover, and less surface skimming for the same flow as compared to the toothless overflow


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Old 06/25/2008, 12:13 PM   #10
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As mentioned above, snails will crawl right over most toothed configurations and most overflow prone fish and shrimp will go right through the teeth

More often than not, the teeth serve no purpose other than eye candy. They are popular because they look nice, not because they perform any critical function.

That said, on some setups with narrow overflows and HIGH flow, they do keep larger fish out of the box. However, in that same case, the surface skimming will be dismal and the entire overflow design should be rethought In other words, if you NEED teeth to keep the big stuff out, then the overflow is more than a little inadequate for the flow you intend to put over it.


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Old 06/25/2008, 02:33 PM   #11
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Add me to the "toothless" list.


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Old 06/25/2008, 03:28 PM   #12
cpeisher
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thanks, i'm going to go with a smooth top coast to coast. With that said, how far below the top rim of the tank should the lip of the overflow be?


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Old 06/25/2008, 03:43 PM   #13
scbauer
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I'll chime in here... I have had teeth on my overflow boxes for years, and just finished building my first tank with a flat (toothless) overflow. I only have about 300 GPH going through the overflow, so it is VERY low flow, but so far I love it.

I actually ran the tank for the first time last night with water, sump, filter sock, etc... Due to the construction of the tank, there was a WHOLE LOT of crap in the water (saw dust, PVC shavings, etc). When I woke up this morning, I would say that about 90% of the crap was gone. I attribute this to having a good closed loop that keeps things suspended in the water column and good surface skimming that allows the crap to be brought down to the sump and removed from the water.

Add me to the toothless club.

As for how far from the top of the tank you want your overflow, that really depends on the look you want. My tank was a standard All-Glass type tank with a 1" black plastic rim. I didn't want the water to be visible below the black plastic rim, so the top of my overflow is right at the bottom of the black plastic rim. The water flows about 1 or 2 mm over the top of the overflow, so it's perfect!

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Old 06/25/2008, 05:34 PM   #14
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I did teeth on my 50g w/ external overflow, and I have to say I fish plenty of snails and more hermits out of my overflow. I havent had any fish go over, but I also dont have many (3-5 at any one time).

I say for nutrient reduction purposes, go toothless. If you have a prized fish, teeth may be more worthwhile...but dont count on them stopping it.


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Old 06/25/2008, 10:07 PM   #15
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I'm teethless and just add black eggcrate still looks clean and nothing goes in.


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Old 06/26/2008, 12:08 AM   #16
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toothless


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Old 06/26/2008, 05:48 AM   #17
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Seems like you could have the best of both worlds by making a horizontal barrier above the coast to coast toothless overflow. The horizontal barrier could be just above the surface of the overflowing water ( say, about the typical width of the space between teeth) allowing unobstructed water flow but still doing the work of the teeth in keeping the fish contained. You could cut inverted teeth in the barrier to allow for flow into the overflow should something obstruct the coast to coast flow.



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Old 06/26/2008, 06:31 AM   #18
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I had contemplated doing exactly that for my 75G coast-to-coast. I had a starry eyed blenny that would NOT stay in the tank. In the end it was just too much trouble My design rested on the trim where the glass panels normally would go. It used nylon thumbscrews to adjust the height. It never got fabricated.

If I build another tank, that will certainly be something that I consider.


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Old 07/09/2012, 07:07 AM   #19
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I just built my first toothless overflow out of glass. I did this after researching the pros and cons of each and I could not be happier. It is a lot quieter than the toothed design and IMO it looks far better.


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Old 07/09/2012, 10:50 AM   #20
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I've got a toothed overflow and have not had a problem. The water is less than a 1/4" deep going over and the teeth extend a good 3/4" above the water line. I also did something similar to what yousmellfishy described except I put a straight piece of acrylic on top of the teeth. I attached some screen to this and used it to cover the overflow box. My teeth are spaced 5/16" apart which will make it really tough for anything to get out and with the straight acrylic and screen on top nothing will go over, either.

As far as optimizing surface skimming goes, I think you would just need a longer perimeter on your overflow to get the same effect (water depth) as a toothless design. Mine has been working for a year and it's never failed me.


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Old 07/09/2012, 12:30 PM   #21
d2mini
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My 7ft toothless C2C overflow skims like mad! Love it.

Hate toothed overflows. Always getting algae and stuff in there. Looks like me after I eat a spinach salad.


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Old 07/09/2012, 12:44 PM   #22
BigAl2007
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My 7ft toothless C2C overflow skims like mad! Love it.

Hate toothed overflows. Always getting algae and stuff in there. Looks like me after I eat a spinach salad.

LOL ! Dennis that was too funny!!

I've had TOOTHED for years and can tell you for sure NO MORE TEETH for me!! Smooth all the way! Been there done that toothed thing and I'm done!!


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Old 07/09/2012, 01:33 PM   #23
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As far as the noise goes, isn't it more a function of how far the water falls inside your overflow box? The level in my overflow is about an inch lower than the tank which keeps things pretty quiet. I suppose if the water level is considerably lower you would get the sound of a bunch of small weirs pouring in instead of a single large one....


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Old 07/10/2012, 11:28 PM   #24
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Originally Posted by super_steve85 View Post
As far as the noise goes, isn't it more a function of how far the water falls inside your overflow box? The level in my overflow is about an inch lower than the tank which keeps things pretty quiet. I suppose if the water level is considerably lower you would get the sound of a bunch of small weirs pouring in instead of a single large one....

Partially. But with teeth you get more of a peeing action which causes the water to separate from the weir and land out in the overflo box instead of sliding down the wall. You can certainly have the same issue with a smooth weir but you need about twice the flow per in before you have that happening with a smooth one.

But to me the biggest advantage is that it's easier to modify and to hit your target first time with a smooth weir. I've often been tortured by toothed weirs causing so much restriction that the tank level was shockingly higher than expected.


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Old 07/11/2012, 12:39 AM   #25
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I prefer toothless, but in my tank it did do the job and keep the fish as well as snails out.


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