Overflow ?

[cichlidtx]

I'm getting ready to make an overflow box for my new 40br tank and was wanting to get opinions on the whether to cut teeth or not. I've read that there beneficial for keeping snails and fish out, but is there another purpose. I can make a lid for the box without teeth and leave a 1/4 " gap for the water flow through. I like the zero edge look as I have seen some members tanks that have it and they look great. I just want do my research before I start cutting or yet, realize after my tank is full of water that I should have done it another way. What your thoughts on this?

[Degener8]

teeth are an easy snail guard.. no other reason for em that I am aware of other than keeping out things that should not be sucked into your overflow

[bitts]

Skimming is more affective with out teeth. They also incress the needed size of the overflow box to acheive the same size weir. Use a slit to form the weir for best results.

[franklypre]

I prefer the teeth, I wasn't aware this lowered skimming ability? Always thought it would help prevent snails, fish and anything else from swimming into the overflow. I'm curious about the skimming thing now, however Bitts probably knows best.

[bitts]

The thing with teeth is there's trade offs. That have to do with the flow rate & type of fish. Like clowns can't swim as well as other fish. so with out teeth a high flow may be problematic. But with out teeth the entire length of the overflow can be used for the weir. Evectively lowering the flow rate at any given point along the weir. This reduces turbulence & allows for better skimming.

 

So with smaller tanks like ours. maximizing the effective skimming ablity while minimizing the size of the overflow is paramount to water quality.

 

Best example I can think of to point out is. Wait let me find it.

[bitts]

Here you go

http://www.nano-reef.com/forums/index.php?showtopic=163883

 

Main point is that water flowing over the weir should be as thin as posable to maximizing skimming. Then this flows directly into the skimmer.

[cichlidtx]

bitts, thanks for the link and the your help. That is similar to what I think I'm going to do. I will make lid that will leave about 1/4" slot. I see your in CO, I lived in Longmont for 2 years before coming to Texas. I'm from the Springs and miss the area. Thanks, again.

[jeremai]

Here you go

http://www.nano-reef.com/forums/index.php?showtopic=163883

 

Main point is that water flowing over the weir should be as thin as posable to maximizing skimming. Then this flows directly into the skimmer.

you say 'maximize' as if overflows with teeth don't skim well. the difference in a small tank is negligible. overflows with teeth skim the surface of the water, as do overflows without teeth. a 5-10% increase in effectiveness, say, will be unnoticeable.

 

to the OP, it's more an aesthetic issue than a functional one. do what looks best to you.

[bitts]

Jer

Its not an issue of one works while the other does not. But the rate of nutrient/ desolved organic solids build up. If it is an improvement of 10% than how is that not worth while. Improvement may by them selves not show a spectacular result. However the cumulative affect of several improvements can result in a tank that is easier to maintain. While planning a system why not maximize the effectiveness of all aspects of that system, when the nessasry steps are relatively easy. Even if that is only a 10% inprovement.

 

 

Edit:

Sorry if I'm being snippy jer. Tend to be a fundamentalist about system design.

 

cichlidtx I'll try to behave better in your thread. Sorry

[C-Rad]

Its not an issue of one works while the other does not. But the rate of nutrient/ desolved organic solids build up. If it is an improvement of 10% than how is that not worth while. Improvement may by them selves not show a spectacular result. However the cumulative affect of several improvements can result in a tank that is easier to maintain. While planning a system why not maximize the effectiveness of all aspects of that system, when the nessasry steps are relatively easy. Even if that is only a 10% inprovement.

I agree with Bitts, but I'm skeptical that the absence of teeth would provide even a 10% improvement. Even so, if the cost of having no teeth is zero, why take the chance that I'm wrong, just play it safe and lose the teeth. On the other hand, if the cost (risk) of having no teeth is not trivial (I keep an octopus (escape artist) so teeth are mandatory to prevent a jail break) then it would be nice to quantify the value of not having teeth. Here's my reasoning, let me know if you see any problems with it.

 

I've heard the argument that says that if there are no teeth, then more surface water vs non-surface water goes over the overflow than if there are teeth. That seems intuitivly obvious because if 50% of the width of the overflow is teeth and 50% is the space between teeth, then it's like having an overflow without teeth that is 50% as wide (skims half as much surface water). I'm skeptical about that line of reasoning. Let's look at it from the point of view of a tiny particle of the scum in my tank. If I'm a tiny particle of scum floating around in my tank, eventually I'm going to touch the surface, where I'll tend to stick to the surface (for the same reason that scum sticks to bubbles in a protien skimmer). Lots of my buddies are all around me because scum like us tend to collect on the surface. We're all floating slowly toward the overflow, but non of us knows if it has teeth or not (i.e., just as much scum collects on the surface regardless of teeth/no teeth). When I get to the edge of the overflow, if there are no teeth I see the top edge of the overflow at about 1/8" deep as I go over the falls. If there are teeth (say 50% teeth 50% gaps) then I hit some turbulence when I get really close to the overflow. I notice that the water current doubles in speed, and I see about half of the other scum balls being pulled under the surface, it looks like all of us get sucked between two of the teeth by the current. I notice that the water is 1/4" deep as I go over the edge of the overflow (twice as deep as when there are no teeth, and double the flow speed, but the same total GPH). I suppose a few scum balls might have been caught up in little eddy currents behind the teeth, and moved around in a circle for a while before flowing, still on the surface, between the teeth, but I can't see how any of them could have escaped being sucked between the teeth. They were stuck to the surface, and by the time they hit the turbulance just before the falls, the same double-speed current that sucked half of them under water, would have pulled them between the teeth. Where else could they go once they got into that current? I suppose that in all the chaos, by some miraculous stroke of luck, one or two of my fellow scum balls that happened to be at the very edge of the churning mob, might have switched places with an innocent little piece of clean water and escaped, but how often could that happen?

 

My main point is that the GPH cycled through the tank will be the same regardless of teeth/no teeth, and that just as much scum will float to, and stick to, the surface of the tank regardless of teeth/no teeth. Given that, the question becomes: How often will a particle of scum, stuck to the surface, that reaches the overflow avoid being sucked between two teeth? I can't see it happening much, and certainly not the 50% of the time that intuition might suggest.

[bitts]

Right, its a low % that gets mixed back in. But the number of times I saw a piece of food almost get sucked into the drain but somehow avoid it is what got me started in all of this weir stuff. so. There's that. This % being low is why there is only a sublte incress to skimming.

 

The other thing is that the boundary layer at the surface is the most important part. While making up a relatively low % of the total water, passing over the weir. The lower the flow becomes at any given point along the weir. The greater this % becomes. Think how much of a difference there would be with a water height of 5/8 vs 1/16 above the weir. There's a bunch of math you can do to figure this % out but its pretty self explanatory once you get the hang of it. If your interested there are links in my sig. Anyway this combined with running the drain directly into the skimmer. Is the best improvement I know of to prevent doc from entering the nitrogen cycle after proper turnover has been established. Note that turn over should have nothing to do with the drain rate. Even with out a skiimer this will move the blah to the sump for the next water change.

[cichlidtx]

I appreciate all the responses and the detailed info. I think I will go without the teeth just for aesthetic purposes. My next question is how large should I make the overflow box. My plan was to drill two holes for 1" bulkheads and use one for primary and the second for safety. Let me know what you think on this as I haven't done anything at this point, just planning and buying. I need to follow bitts sig, Propperly designed tanks lead to happy wifes & dry floors. Thanks again for the help.

[bitts]

The needed lenght for any overflow to improve skimming, will be based on the expected flow rate. Assuming that the goal is to keep the water height under a set amount. Detrimen that height & then find the rate of flow that is posable for that height without the water line rasing above the drain point. Aka how much water can pass through a 1/4 hole without rasing above it. Then divide the expected flow by this rate to find the needed length.

[bitts]

Drain rate calculator

 

http://www.grow.arizona.edu/Grow--GrowReso...?ResourceId=188

 

Also does a really good job of explaining the math. For 300 gph 12 inches should work. Any more flow than that could be supplemented with vortechs or korilla's, or increasing the weirs length. 15" would push it to about 400gph.

[cichlidtx]

bitts thanks for the link. I found a flow rate of 480gph using a 1" hole at a depth of 2". Do you think that 2" depth is ok? If so, then a it looks like about an 18" length should work. I was also wondering if the height of the box would affect anything? My plan for box size was 18"L x 5"W x 4"D. I appreciate your help in figuring this out, I just want to get it right before drilling and adding water.

[bitts]

18 x 5 x 4. Sounds like a coast to coast with bean animals fail safe drain setup. From rc's diy forum. Is a good setup. At 2 inched there may still be air sucked into the Primary drain. Which is the point of beans setup. Allows for the secondary drain to be used to drain a minute amount. Keeping the main fully submerged. Then the third drain is a siphon completely draining the overflow box if it ever engages. I'll find the link.

 

 

http://www.beananimal.com/projects/silent-...low-system.aspx

 

 

Now the same set can be used as a 3 sided overflow box like the one you have described. The drain setup could be true herbie, or bean's improved herbie.

 

I hope that answered some of the question, though I fill that I may have completely skipped it. Let me know if I did.

 

Oh & the height of the box allows for adjustment of the water line with in.

 

Small = little

Large = more

[cichlidtx]

Thanks bitts, I think I will go with this design but I might not do the coast to coast. I think the three sided idea might work almost as well. What do you think?

[bitts]

Personally as far as the coast to coast. I've always thought they should be on the out side. If its inside the tank I like them in the corner to make it easier to get things in & out of the tank. Again personaly I don't like the look of a box on the side of the tank compaird to a full hight overflow. But really type & placement matter only in relation to the weir noise & wether or not there will be a wave splashing into it.

[cichlidtx]

I was thinking of placing it in the back right corner of the tank. If I go 18"L x 3.5"W x 6"H on the box it will only go half way across the back of the tank. This shouldn't occupy to much space but hopefully be sufficient size to skim the water surface. Again, I appreciate your feedback.

[bitts]

Sounds perfect. Depending on plumbing. You may even be able to go from 3.5" down to 3".

[cichlidtx]

Sounds perfect. Depending on plumbing. You may even be able to go from 3.5" down to 3".

Hey bitts, I appreciate your help. It's been slow going but I would like your opinion on my current idea. I like the look of the center overflow and was thinking of using a 24" x 4" x 2.5" overflow. I also plan on using dual 3/4" returns on each side. I did a cardboard mock up to show the layout. Let me know what you think.

 

Thanks,

 

[bitts]

that looks pretty good.

for some reason its making me think about neanderthalmans thread. would be good sorce of info.

http://www.nano-reef.com/forums/index.php?showtopic=145187

 

dont forget to practice before drilling the tank.

[bitts]

update....

[glazer]

I dunno... most the time I think stuff gets way too overengineered. The benefit of the overflow with no teeth promoting better surface skimming ability might have some merit on really large systems, Small ones? Not enough in my opinion to be even worth considering. Is every last ounce of water that went through that toofless weir ending up in your protein skimmer? Maybe if your drain is feeding the skimmer directly but even then you're not pulling all the nasty stuff out with a quick woosh through the PS.

 

Personally I would make the teeth/no teeth decision based more upon what the tank was going to house. Bottom dwelling fish and the majority of my CUC sand and rock based... fine, no teeth. Free ranging snails and free swimming fish... teeth AND a lid. Just so you know, I work part time for an aquarium maintenance business and have off and on for years... not speaking on theory but practical experience. I/we have replaced several "coast to coast" style overflow boxes for those with teeth and lids because of constantly pulling snails and fish out of the boxes. A few shrimp of various species as well.... it's like kids, they can't help it... they want to go where they are not supposed to...lol

 

Steve

[cichlidtx]

I have no updates as I'm waiting on a friend to help out with the drilling. I may just go ahead and go for it. Glazer, thanks for the input on the overflow. I will have to take in consideration my livestock choices before making the overflow as you recommended. I will update as I continue with the build.