what are all the drawbacks of no overflow box?

[geaux xman]

I've seen a few tanks without overflow boxes.

Surface skimming isnt as good, stuff getting caught up in the drains ?
It just seems like if you have a good turnover rate thru the sump and good flow in the tank,
it will work out okay.

Heres Ching Chai's club. 375g tank. 2 big drains and 2 returns.

http://www.reefcentral.com/forums/sh...2166261&page=3

Heres a guy with just 2 drains and 2 returns in the uppper corner of a 400g tank. His reef tank is very nice too.
post #41.
http://www.reefcentral.com/forums/sh...2063379&page=2

[Nicodemus85]

I am currently in the middle of deciding between and overflow box or drilling a hole in the glass of my 70gal bowfront to create and elbowed stand pipe. Interested to see what people say here....

I guess both will still keep your sump from overflowing in a power outage..maybe the surface skimming just looks cleaner?

[BeanAnimal]

Regardless if the turnover, you really need to have surface skimming... The air/water interface is where organics are bound to the surface tension of the water and react to the air. We don't want them to get churned back into the water column where they can be used or absorbed by nuisance algae. We want them taken to the filtration system.

You will find that even with a high turnover, surface scum can quickly build up. This decreases gas exchange at the surface and reduce the light available to the corals by reflecting/refracting and absorbing it.

There really is no good reason to do without surface skimming, and there are plenty of reasons to maximize the amount of surface skimming.

[reeftanknewbie]

Originally Posted by BeanAnimal

Regardless if the turnover, you really need to have surface skimming... The air/water interface is where organics are bound to the surface tension of the water and react to the air. We don't want them to get churned back into the water column where they can be used or absorbed by nuisance algae. We want them taken to the filtration system.

You will find that even with a high turnover, surface scum can quickly build up. This decreases gas exchange at the surface and reduce the light available to the corals by reflecting/refracting and absorbing it.

There really is no good reason to do without surface skimming, and there are plenty of reasons to maximize the amount of surface skimming.

Well played BeanAnimal....you explained it perfectly. That's why I love the coast to coast overflow.

[Preston7]

You're better off with a small overflow box, than none. Heck, go external if you can and have the best of both worlds!

I'm not a firm believer in hindering the filtration process; especially with something like this.

[Detroit_306]

I didn't use one and have to blast power heads at the surface because of the film

[wildman926]

I use overflow boxes and churn the surface with the return flow and a spray bars on both my tanks. Light enters the skimmer portion and grows hair algae. The water flows over the hair algae creating a mini ATS. Works pretty well.

[LobsterOfJustice]

I ditched overflow boxes and never looked back. I'll copy and paste something I wrote in another thread about the topic:

I hate overflow boxes, I say rip it out. I'll never have another overflow box again, they take up so much space and can't be kept clean. I drill my tanks in the upper back corners and put an upturned elbow in the bulkhead, paint it to match the back of the tank and it's invisible and takes up no useful real estate... and its removable so you can soak it in vinegar to get it looking clean as new.

Here are examples of my overflowless tanks

90g (the urchins have chewed some spray paint off the elbows... takes an hour to pull them out, spray them new, and put them back in)


180g (powerheads are directly adjacent to the overflow elbows)


90g I'm currently setting up (hadn't painted the elbows black yet in this picture)


Contrast this to my first tank, a 75g reef ready. Yeah, the tank looks alright, but compare it to the above pictures and think about how much better it would look without that huge eyesore!


Getting rid of overflow boxes is IMO a simple and huge step you can do to take your tank to the next level, it opens up so much more space and makes the tank so much cleaner and... "professional". Several years ago I noticed that all the nice looking tanks I saw online didnt have pesky internal overflow boxes (and certainly not ugly offset plastic ones that you can't scrape the coralline off of), so I started drilling my tanks this way and never looked back...

[cpt cautious]

I agree that surface skimming is needed, maybe try an external overflow if its really just the aesthetics that are bugging you. I dont know how easy it would be to cut slits in the glass to diy, but it would give you best of both worlds

[LobsterOfJustice]

I don't understand - why do people think an upturned elbow in each back corner will not provide adequate surface skimming? I've never had anythying close to a film on the surface of my water.

[BeanAnimal]

Originally Posted by LobsterOfJustice

I don't understand - why do people think an upturned elbow in each back corner will not provide adequate surface skimming?

Physics...

Removing overflow boxes is taking your aquarium to the next level? Respectfully, even a broken clock is right twice a day

That is, you are entitled to your opinion, but your reasoning is contrary to hard science and the laws of physics. In general, lack of surface skimming allows organics to bond and stay on the surface. If there is enough flow to keep them churned in, then they are harder to export via other means of filtration and far more apt to become food for algae. This is not up for debate, it is simple physics.

[dryworm]

do a calfo coast to coast overflow with bean animal setup.

[rick12]

Originally Posted by LobsterOfJustice

I don't understand - why do people think an upturned elbow in each back corner will not provide adequate surface skimming? I've never had anythying close to a film on the surface of my water.

I only have one elbow in my 90g? Didn't know any better when I setup the system. Years old now and like it!

Originally Posted by BeanAnimal

Physics...

Removing overflow boxes is taking your aquarium to the next level? Respectfully, even a broken clock is right twice a day

That is, you are entitled to your opinion, but your reasoning is contrary to hard science and the laws of physics. In general, lack of surface skimming allows organics to bond and stay on the surface. If there is enough flow to keep them churned in, then they are harder to export via other means of filtration and far more apt to become food for algae. This is not up for debate, it is simple physics.

I have always kept a power head pointed to the surface to keep it agitated.

[LobsterOfJustice]

Originally Posted by BeanAnimal

Physics...

Removing overflow boxes is taking your aquarium to the next level? Respectfully, even a broken clock is right twice a day

That is, you are entitled to your opinion, but your reasoning is contrary to hard science and the laws of physics. In general, lack of surface skimming allows organics to bond and stay on the surface. If there is enough flow to keep them churned in, then they are harder to export via other means of filtration and far more apt to become food for algae. This is not up for debate, it is simple physics.

I'm not debating physics, I can only imagine you are not understanding what I am saying. You can either skim the surface with an overflow box placed around a drilled hole in your tank, or you can extend a pipe from that hole to the surface and water will overflow into that pipe in exactly the same way in overflows into an ugly plastic box.

[geaux xman]

the guys tank in the OP. it doesnt look like it is suffering too much from not having an overflow box.

[propeine]

Its the area to volume ratio of the water that is skimmed though. The larger the overflow length the thinner the "thickness" of the water is skimmed. If you have 2" over overflow and are moving 100ci/min of water, that water has to be higher above the overflow than if you have 10" of overflow. If all the scum is on the top 1/32" then why would you want to overflow water from deeper than that? Sure there are reasons due to constraints etc and even aesthetics but that is why a longer overflow is better than a shorter.

[LowerUnit]

Lobster - do you use slip elbows or threaded?

[LobsterOfJustice]

Originally Posted by geaux xman

the guys tank in the OP. it doesnt look like it is suffering too much from not having an overflow box.

Agreed, I think you will feel the same about the photos of my tanks above.

propeine, I don't think the only dirty water in my tank is in the top 1/32 of the tank, though I'm sure some of it concentrates there. Also, two 1.5" elbows offers almost 9.5" of linear overflow surface. You can only skim the surface so much... it's either skimmed, or not. There comes a point when more isn't necessary. I guess I feel that limit is a lot lower than most other people? If I put flakes anywhere on the surface of my tank they are down the overflow in a matter of seconds, seems good enough to me.

Lowerunit, either is fine... I've used threaded in the past but I'm using slip now because it's easier to adjust them to a upright position while also being snug (sometimes with threaded its a little loose while upright but one entire turn around would be too tight).

[propeine]

Originally Posted by LobsterOfJustice

Agreed, I think you will feel the same about the photos of my tanks above.

propeine, I don't think the only dirty water in my tank is in the top 1/32 of the tank, though I'm sure some of it concentrates there. Also, two 1.5" elbows offers almost 9.5" of linear overflow surface. You can only skim the surface so much... it's either skimmed, or not. There comes a point when more isn't necessary. I guess I feel that limit is a lot lower than most other people? If I put flakes anywhere on the surface of my tank they are down the overflow in a matter of seconds, seems good enough to me.

Lowerunit, either is fine... I've used threaded in the past but I'm using slip now because it's easier to adjust them to a upright position while also being snug (sometimes with threaded its a little loose while upright but one entire turn around would be too tight).

I agree with you that there is a point of diminishing returns for sure! I also agree that the dirty water is in more than the top 1/32". Scum just seems to congregate towards the top so the concept of more is better leads people to believe you need as much overflow area as possible. There is even a calculator on RC that offers an optimum overflow length. I never looked into the math of it though. I was just explaining the reasoning not trying to add argument in either direction honestly.

I went with a C to C overflow and have 22". Is it overkill? Definitely. Is it hurting anything other than losing some display area in the back? Maybe...it interrupts my flow in ways that irritate me but oh well.

Some people question the use of slits and say it reduces effectiveness of skimming. This would go hand in hand with too little linear overflow area. I opted to use no slits and go the full 22". Obviously your 9.5" is working out just fine. I think RC recommended mine at 7" tbh but i didnt like how closely that put all my bulkheads so spaced it out.

Additionally I'm not sure how easy/hard it would be to get a "BeanAnimal" style overflow to work without some sort of box. I never really thought about it to be honest. If I eliminated my box my DT water level would drain significantly farther than it does now which would cause my sump to flood. You would have to have a pretty deep elbow to keep full siphon on an upturned elbow I would think and not have it suck air at all. That alone is enough reason for me not to change but could have been set up differently from the start.

[BeanAnimal]

Originally Posted by rick12

I only have one elbow in my 90g? Didn't know any better when I setup the system. Years old now and like it!



I have always kept a power head pointed to the surface to keep it agitated.

So that the organics can be mixed back into the water column where they can be easier used by nuisance algae instead of by your filtration system in your sump

[BeanAnimal]

Originally Posted by LobsterOfJustice

I'm not debating physics, I can only imagine you are not understanding what I am saying. You can either skim the surface with an overflow box placed around a drilled hole in your tank, or you can extend a pipe from that hole to the surface and water will overflow into that pipe in exactly the same way in overflows into an ugly plastic box.

No...

The AMOUNT of surface skimming is a function of the flow and length of the weir. That is, for a given rate of flow, the longer the weir, the greater (more efficient) the effect of surface skimming.

[BeanAnimal]

Originally Posted by LobsterOfJustice

Agreed, I think you will feel the same about the photos of my tanks above.

propeine, I don't think the only dirty water in my tank is in the top 1/32 of the tank, though I'm sure some of it concentrates there.

The "dirty water" concentrates there because it reacts with the oxygen at the air/water interace and is bonded by the surface tension. The idea is the renew this surface as quickly as possible and get the concentrated, but already dislodged organics quickly to the skimmer where than can be more easily removed.

Also, two 1.5" elbows offers almost 9.5" of linear overflow surface. You can only skim the surface so much... it's either skimmed, or not.

No... The thinner the sheet of water, the faster the surface is renewed. It is about exposing water more quikcly to the air/water interface and then getting it to the filter.

Is there a point of diminished returns? Sure... How big is the tank, what is the flow rate over the weir, etc.

The overfflow calculator on the RC home page takes a few of these variables into consideration and spits out a minimum weir length based on some basic assumptions regarding the efficiency of surface skimming and what we know about surface renewal.

This science is used daily worldwide to size weirs for wastwater treatment, aquaculture farms, treatment ponds, etc.

[Tmoriarty]

If you had an overflow box with 18 inches of length but only 18 1/4" slits in it you would skim less surface then a 1.5" elbow with now slits.

I think the best option is a Coast to coast with no slits to impede surface skimming.

[BeanAnimal]

You in fact end up with FAR LESS than 18 x 0.25" of linear weir, as the surface tension and turbulance at each tooth further impede flow and thicken the headwater. Subtract maybe 30% for the .25" teeth. That is, an effective linear weir length of maybe 3"

[LobsterOfJustice]

Originally Posted by BeanAnimal

The "dirty water" concentrates there because it reacts with the oxygen at the air/water interace and is bonded by the surface tension. The idea is the renew this surface as quickly as possible and get the concentrated, but already dislodged organics quickly to the skimmer where than can be more easily removed.


No... The thinner the sheet of water, the faster the surface is renewed. It is about exposing water more quikcly to the air/water interface and then getting it to the filter.

Is there a point of diminished returns? Sure... How big is the tank, what is the flow rate over the weir, etc.

The overfflow calculator on the RC home page takes a few of these variables into consideration and spits out a minimum weir length based on some basic assumptions regarding the efficiency of surface skimming and what we know about surface renewal.

This science is used daily worldwide to size weirs for wastwater treatment, aquaculture farms, treatment ponds, etc.

So it seems we just disagree on how much "length of weir" is necessary, and where that point of diminishing returns is. I've never had a film on the surface of my water, and flake food on the surface of my water makes it to the overflow in a matter of seconds... thats renewing the air/water interface fast enough for me.