# Hooking up canister to overflows?



## aspects (Dec 27, 2009)

no.
canisters run off of a closed siphon. quite the opposite of an overflow. if you plan to use a canister,. your best bet is to cap the holes for the overflow. 
but if the tank is already drilled, why not just use the overflows and build a sump?


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## odie (Dec 29, 2009)

I was debating the sump. Just afraid of off gassing of CO2.


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## enzo (Aug 21, 2006)

Hello, I have a 65g w/ megaflows hooked up to a Marineland canister filter. Previously this was a reef tank but now this aquarium is for my roomates Oscars.

I kept the 'return to tank' of the megaflow in place. Then I removed the 'adjustable drain' part. Both the incoming and outgoing sizes are 3/4 inches so they fit onto canister filter very well. Due to evaporation, the water level in your megaflow will be the first to drop so you'll need to top it off every now and then. I also like that I could hide the heater in there. 

Also, if you keep the water level in the megaflow relatively high then, co2 gas off would be minimal.

I could get some pictures if that would be helpful.


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## odie (Dec 29, 2009)

yes pics please. I am a bit confused by this. I am not sure what the adjustable drain is. I basically have two large overflows and 4 holes in the bottom of the tank.


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## OverStocked (May 26, 2007)

aspects said:


> no.
> canisters run off of a closed siphon. quite the opposite of an overflow. if you plan to use a canister,. your best bet is to cap the holes for the overflow.
> but if the tank is already drilled, why not just use the overflows and build a sump?


Wrong.

The way you hook them up using overflow boxes woudl work just fine. I have seen it done several times.


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## wkndracer (Mar 14, 2009)

Several members have strings including conversions that use canisters. I stayed with a DIY sump configuration and out gassing is not as huge an issue as most believe. sunfire99 along with others run both a sump and canister in combination.


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## Burks (May 21, 2006)

Never thought of doing this. If anyone has photos, I would love to see them!

The reason I haven't set up my 65g is I don't want to have a sump, simple as that. It's drilled and I really don't feel like capping that off when I can actually use it (and keep the tank a little "cleaner" looking).


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## lauraleellbp (Feb 3, 2008)

If you plumb a canister to an overflow you should probably drill some holes lower down in the overflow to minimize the risk of the canister's motor burning out in case the tank's water level falls beneath the top of the overflow. (Though I know some overflows are designed with intakes at the bottom so that obviously wouldn't be an issue in that case.)

The first 90gal I had was drilled with a DIY overflow... I eventually decided to get rid of that tank and just go with canisters so I wouldn't have to try and find a way to hide the overflows and deal with them, since I didn't want a sump.

It's just a matter of deciding which direction you want to go, and making it work for you.


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## aspects (Dec 27, 2009)

over_stocked said:


> Wrong.
> 
> The way you hook them up using overflow boxes woudl work just fine. I have seen it done several times.


it seems as though you have a severe misunderstanding of the function of an "overflow".


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## Burks (May 21, 2006)

Actually just thought of this, probably matters on what *kind* of overflow you are running as well. The over the back type I can see causing issues with air going into the canister. That's just my experience, always noticed tons of bubbles in my sumps with that kind. 

Now if you have an overflow that isn't like that (just basically PVC coming out of a bulkhead), I've found they produce much fewer bubbles. Again, my experience. This may have less of an impact on the canister as less air *should* get in it. Who knows....... I may very well be way off here.


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## odie (Dec 29, 2009)

enzo said:


> Hello, I have a 65g w/ megaflows hooked up to a Marineland canister filter. Previously this was a reef tank but now this aquarium is for my roomates Oscars.
> 
> I kept the 'return to tank' of the megaflow in place. Then I removed the 'adjustable drain' part. Both the incoming and outgoing sizes are 3/4 inches so they fit onto canister filter very well. Due to evaporation, the water level in your megaflow will be the first to drop so you'll need to top it off every now and then. I also like that I could hide the heater in there.
> 
> ...


So has anyone else done this? Pictures?


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## enzo (Aug 21, 2006)

Hello sorry for the delay. I gathered some more info and the photos for you.

Typically, the megaflow is setup as such: 


1inch drain installed with adjustable "J" drainpipe
3/4inch return installed to t-nozzle

Reference the photo in the link below:
http://www.drsfostersmith.com/product/prod_display.cfm?pcatid=12078

To make it work with a canister filter do the following:

Remove adjustable "J" drainpipe
Switch out 1inch drain to the 3/4inch drain
Then connect the drain and the return on the underside of the tank to your canister filter (your connections may or may not be plug and play--you can always go to a hardware store to get tubing adapters to make the connection work).
Fill the overflow box up to near the top
Finally turn on your canister filter. The water level in the overflow box will begin to drop slowly while the canister filter is priming and soon thereafter the flow will be constant. Be sure to top off the overflow box.

As mentioned before the water level in the overflow box will be the first to drop due to evaporation (top off the overflow twice a week). You can minimize co2 gas off by keeping the water level in the overflow box rather high. A benefit of the overflow box is that you can hide equipment such as a heater in there.

I don't know if you canister filter has this feature but the doubletap connectors are ideal as they make servicing the canister filter very easy--simply close valve--clean filter--then reconnect filter and open valves and it will prime automatically. The link below shows a picture:

http://www.drsfostersmith.com/product/prod_display.cfm?pcatid=6688


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## enzo (Aug 21, 2006)

I just realized you have twin overflows. If that is the case, you will want both overflows to operate identically. Be sure to get the same model filter for each overflow and keep the tubing length(in and out) identical for both.

You should also put them on one power strip and no matter if you need to service one or the other, shut off the *power strip* so the power is pulled from them at the same time. This should keep you water levels in the overflows balanced.


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## FSM (Jan 13, 2009)

aspects said:


> it seems as though you have a severe misunderstanding of the function of an "overflow".


It is you who is mistaken.

It won't technically be an overflow, but it still works.

If the tank is full, the overflow no longer functions as an "overflow" and the canister can be attached to the bulkhead with zero problems.

Even if the tank isn't full, as long as there is enough water in the system to keep the drain from sucking in air, there won't be any problems. It is extremely unlikely that this would happen, because if the drain is at the bottom, the overflow would need to be nearly empty. This won't happen, because all the water that drains out of the overflow flows back in.
Air bubbles produced might get sucked in, however, so it's best to keep the tank filled above where it would normally be with a sump.


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## inkslinger (Dec 28, 2003)

I had run my 110g tank with a Eheim 2028 for years . When I bought my tank used , the person who had it first drill the bottom for intake and return. I reduce the bulk heads to attach the Eheim hose. So now for this year I cap off the the tank with bulk heads with caps.


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## FSM (Jan 13, 2009)

inkslinger said:


> I had run my 110g tank with a Eheim 2028 for years . When I bought my tank used , the person who had it first drill the bottom for intake and return. I reduce the bulk heads to attach the Eheim hose. So now for this year I cap off the the tank with bulk heads with caps.


Why?


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## odie (Dec 29, 2009)

OK I am revisting this. My question is I have two overflows and would need to use two canisters. I would take the "J" return pipe off and connect the drain line to the bottom of the tank. The return from the canister would go from the tubing to the megaflow retrun.

Would running two canisters be a problem? I cant imagine it would as I think it would be in essence be the same as running a normal canister.


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## 150EH (Dec 6, 2004)

I was looking at 2 tanks today with overflow boxes in the corners, why can't you just remove the overflows and use bulkheads??? Like Inkslinger said, what i saw could easily be removed and you would get much more room in the tank and use your canisters with no problems, I don't see any reason for the overflows in a freshwater tank, but I'm not very familiar with that setup. Two canisters would be a bonus and there's four holes, right.


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## odie (Dec 29, 2009)

Yes four holes. Benefit is you could get an overflow action that will pull alot of the organic waste aka the oil slick you will see on the top the tank water. 

As far as removing them the problem is they are siliconed in and where they cross the normal silicone around the framing (especially at the bottom). When removing might remove the frames silicone.


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## Centurion (Jun 5, 2011)

odie said:


> OK I am revisting this. My question is I have two overflows and would need to use two canisters. I would take the "J" return pipe off and connect the drain line to the bottom of the tank. The return from the canister would go from the tubing to the megaflow retrun.
> 
> Would running two canisters be a problem? I cant imagine it would as I think it would be in essence be the same as running a normal canister.


Just like buying a surface skimmer for your canister with the benefit of all evaporation coming out of the overflow and the display always full.


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## odie (Dec 29, 2009)

Centurion that is what I was thinking. I am wondering about the option of going with a large single canister like a Fluval FX5 just "T" thereturns and bulkheads from overflows.


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## Centurion (Jun 5, 2011)

The split in the return I've seen many times and am certain wouldn't be a problem. I'd imagine combining the drains should work as well.


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