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...
Overflow - Teeth or Not
- Thread starter cpeisher
- Start date
Rysam
New member
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.
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?
hyperfocal
Active member
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).
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 will 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.
Shadowramy
In Memoriam
I would go no teeth, you can always clip on some gutter guard later.
BeanAnimal
Premium Member
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
BeanAnimal
Premium Member
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.
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.coralnut99
New member
Add me to the "toothless" list.
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!
-Scott
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!
-Scott
MinibowMatt
Active member
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.
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.
heyfredyourhat
Premium Member
toothless
yousmellsfishy
New member
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.
BeanAnimal
Premium Member
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.
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.
shovelrider
New member
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.
super_steve85
Member
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.
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.
