Overflow Teeth Cutting

[president89]

Hi, I want to make a tank like this, only a 40G breeder. I have all the acrylic ready to go in, the last step is to put the teeth in. I want one return, and one Drain. The plan was to put teeth along the bottom of each chamber or to alternate them top/bottom/top/bottom to ensure the water is fully flowing through each compartment.

1. Can I cut the teeth with my table saw - I have a blade that I cut acrylic with.

2. How long should the cuts be for 17.5 wide tank. And how far spaced - I was thinking 1" spacing giving me 17 slits.

3. What's the best way to ensure my teeth are all the same length - prevent the table saw cutting too deep. I was going to put painters tape, and watch that to ensure i wasn't cutting too far.

 

[uncleof6]

Teeth reduce the surface skimming/surface renewal capability of any overflow system by 1/2 to 2/3. Also the channeling caused by the teeth, is a source of unnecessary noise. Neither of these conditions is good for a system.

More functional and better performing systems utilize a flat weir with no teeth. It is far better for the system as a whole, just does not look as cool...

 

[rwb500]

i agree, teeth are always a bad idea. a flat weir is best, and if you need to keep fish out, use a mesh like gutter guard. Overflow teeth were a bad idea that just took off somehow.

 

[SkullV]

Teeth reduce the surface skimming/surface renewal capability of any overflow system by 1/2 to 2/3. Also the channeling caused by the teeth, is a source of unnecessary noise. Neither of these conditions is good for a system.

More functional and better performing systems utilize a flat weir with no teeth. It is far better for the system as a whole, just does not look as cool...

Look as cool and prevent fish/snails from entering your drain plumbing. I have had systems with and without teeth, will never go without again. If you have an issue with your overflow teeth preventing you from running the return pump your system needs, then you need a bigger overflow. Has never been an issue for me though.

 

[SkullV]

i agree, teeth are always a bad idea. a flat weir is best, and if you need to keep fish out, use a mesh like gutter guard. Overflow teeth were a bad idea that just took off somehow.

Why? In a 75g for example, you can run an Eheim 1262 wide open with a standard megaflow overflow (built in teeth). In what situation do you need more flow than that going to and from your sump?

 

[president89]

My thread title is poor. I want to put the teeth facing DOWN under the water as seen in the pic. The teeth cutting for an overflow would simply be the same. Apologies for confusion.

 

[Gorgok]

What purpose are the dividers there for? Make separate 'tanks' in the tank that still share the same water? To keep fish separated? Permanently or temporarily? What size of thing does the divider need to block?

 

[uncleof6]

Look as cool and prevent fish/snails from entering your drain plumbing. I have had systems with and without teeth, will never go without again. If you have an issue with your overflow teeth preventing you from running the return pump your system needs, then you need a bigger overflow. Has never been an issue for me though.

I have run both as well, and I have found, that the performance of the system is more important. Teeth will not prevent a determined speciman from getting into an overflow/drain system. Some may wish to argue that, and that is fine. In 35 years I have had two fish go down the drain, and they both wound up swimming in the sump, happy as could be. The 'danger' is highly exaggerated...

In terms of surface skimming/surface renewal (e.g. system performance,) the physics of how weirs work, (flat weir vs toothed weir,) shows that flat weirs perform the essential function needed of an overflow in a far superior manner than a weir with teeth cut in it; that cannot be argued. (head height behind the weir, amount of subsurface water flowing over in relation to surface water flowing over.)

Sure, if the overflow cannot handle the flow rate, you need a larger overflow. Even though that is not the issue here, the effective size of a toothed weir, is (usually) 1/2 - 2/3 smaller than the actual size of the overflow. The effective length is what does the work. (This is the reason that commercial overflows are horribly undersized for the stated flow rate.) The longer the effective length of the weir, the faster the surface layer is removed (skimmed off,) and the faster it is replaced (renewed) and that is very important.

There are other means to keep critters out of the overflow, that do not interfere with the functions of an overflow, if there is really a need for such.

 

[SkullV]

I believe pet co sells premade dividers like that which will work for a 40br. Otherwise your table saw is fine. I prefer to use a table router and set the guard so the depth of every tooth will be the same.

 

[uncleof6]

i agree, teeth are always a bad idea. a flat weir is best, and if you need to keep fish out, use a mesh like gutter guard. Overflow teeth were a bad idea that just took off somehow.

They took off due to marketing hype and 'it looks cool.' This never takes into account the needs of the system.

 

[president89]

What purpose are the dividers there for? Make separate 'tanks' in the tank that still share the same water? To keep fish separated? Permanently or temporarily? What size of thing does the divider need to block?

I want to house separate pairs of clownfish, share the same water, and not need multiple drains and returns. The teeth are simply to let water flow through each chamber.

 

[SkullV]

I have run both as well, and I have found, that the performance of the system is more important. Teeth will not prevent a determined speciman from getting into an overflow/drain system. Some may wish to argue that, and that is fine. In 35 years I have had two fish go down the drain, and they both wound up swimming in the sump, happy as could be. The 'danger' is highly exaggerated...

.

I don't disagree with the performance aspect, although I've never had any sort of surface scum with a toothed weir. Keeping fish out of the sump however is a different story. A toothed overflow with a lid keeps everything you want in the tank there. The one time I ran without teeth and a lid I ended up with a fish in my skimmer intake and multiple fish in my cryptic fuge where it was impossible to remove them.

 

[uncleof6]

My thread title is poor. I want to put the teeth facing DOWN under the water as seen in the pic. The teeth cutting for an overflow would simply be the same. Apologies for confusion.

Same applies, except rather than just poor surface skimming you will have a poor flow rate due to excessive restriction through the slots, and a complete lack of surface skimming/renewal (think removal of dissolved organics, and gas exchange) because there is no flow over a 'weir' or overflow... ?

I think perhaps you need to define exactly what it is you are wanting to do/accomplish...

 

[president89]

I want 5 chambers with 1 drain and 1 return, not 5 drains and 5 returns. This is for FO setup, no corals. Live rock will be in sump.

 

[uncleof6]

I don't disagree with the performance aspect, although I've never had any sort of surface scum with a toothed weir. Keeping fish out of the sump however is a different story. A toothed overflow with a lid keeps everything you want in the tank there. The one time I ran without teeth and a lid I ended up with a fish in my skimmer intake and multiple fish in my cryptic fuge where it was impossible to remove them.

The operative word here is lid... I am sorry your critters bailed on ya, but another thought would be: why did the fish not like it in the DT? Excessive dissloved organics (pollution,) not enough food, and they went hunting for it? Low oxygen? Just sayin... some critters have a reputation for jumping, but there is no satisfactory explanation as to why, and one of the theories is: poor water quality...a parallel would be anemones moving around the tank looking for a more suitable location, getting sucked into a power head because there was not a better location lower in the tank... again just sayin...

You won't see a scum if you are mixing it back down into the tank, rather than efficiently pulling it out of the tank and sending a more concentrated solution to the skimmer...

 

[AcroporAddict]

I don't disagree with the performance aspect, although I've never had any sort of surface scum with a toothed weir. Keeping fish out of the sump however is a different story. A toothed overflow with a lid keeps everything you want in the tank there. The one time I ran without teeth and a lid I ended up with a fish in my skimmer intake and multiple fish in my cryptic fuge where it was impossible to remove them.

Here's one for you. I have a planet aquariums 465 gallon tank, and my overflow is slitted, but not vertically. I have three rows of horizontal slots, with each opening about two inches by 1/4 inch. Not an open weir, but not vertical teeth either.

OP: I slotted my 100 gallon reef tank's plexi overflow with a table saw just like you propose. Your idea of using painters tape and cutting up to it will work. Just keep in mind for aesthetics that since your cutting blade is curved, the underside cut will have a curve to it unless you raise the blade as high out of the table saw as you can. I faced the underside towards the interior of the overflow. Also, if you can do two passes for each slot, the better. I did one per slot, and had to go back after it was in stalled and widen them out with a hand file. Big PIA. You want a minimum width of 1/4" for each slot.

 

[SkullV]

The operative word here is lid... I am sorry your critters bailed on ya, but another thought would be: why did the fish not like it in the DT? Excessive dissloved organics (pollution,) not enough food, and they went hunting for it? Low oxygen? Just sayin... some critters have a reputation for jumping, but there is no satisfactory explanation as to why, and one of the theories is: poor water quality...a parallel would be anemones moving around the tank looking for a more suitable location, getting sucked into a power head because there was not a better location lower in the tank... again just sayin...

You won't see a scum if you are mixing it back down into the tank, rather than efficiently pulling it out of the tank and sending a more concentrated solution to the skimmer...

Must be working ok, undetectable levels, great SPS color, excellent growth, excellent polyp extension. As far as fish jumping, your post is QUITE a stretch, but my best guess would be flow related. I generally run over 100x turnover in my sps tanks. Some fish like it, some don't. Who knows, I don't have 35 years in the hobby, but I did stay at a holiday inn last night.

Edit: Any photos of your system utilizing a non-toothed, 100% fish/snail safe overflow? I didn't see any in a quick search.

 

[laga77]

I am happy I found this thread as I am in the beginning of a new 120 build. I started building the stand today and started practicing glueing the acrylic for the overflow as I will be building that also. I understand the argument on the toothless weir and makes sense to me. If I do go that way do I need to lower the top of the weir in relation to the trim on the top of the tank. My last tank I installed a weir with teeth right at the bottom of the trim. If I do this with a plain weir will that be too high? The overflow will be 24"Lx6"Dx4"W. I plan on gutter guard or a solid lid with either slots or holes.

 

[SkullV]

I am happy I found this thread as I am in the beginning of a new 120 build. I started building the stand today and started practicing glueing the acrylic for the overflow as I will be building that also. I understand the argument on the toothless weir and makes sense to me. If I do go that way do I need to lower the top of the weir in relation to the trim on the top of the tank. My last tank I installed a weir with teeth right at the bottom of the trim. If I do this with a plain weir will that be too high? The overflow will be 24"Lx6"Dx4"W. I plan on gutter guard or a solid lid with either slots or holes.

Yes you will need to set the weir height at the water height you desire, maybe 1/8" below to account for flow over the weir.

 

[AcroporAddict]

Here is a quick pic of my overflow in my 465 gallon. You can see almost two of the three rows of horizontal slots. The third is normally above the water line. Normally the water level is just over the bottom of the middle row of slots, except when my MP60s start a wave.