# How much flow is too much?



## buffheman (Feb 23, 2011)

I just got an Eheim 2215 for my 29gal tall. Previously, I had an AC50... so you can imagine the difference is quite noticeable. I have the intake in the bottom right corner, and the spray bar on the back wall in the top left corner.

I originally had it pointed at the wall, but the flow still didn't seem great. So I pointed it out, and the it was nuts. Not crazy, like the plants weren't getting bent in half or anything, but the fish just looked like they were working really hard. So I just closed a little nozzle just a tad bit on the output hose, and I think I like it now. But two questions...

1) How does one know when your flow is too high?

2) I've read that reducing the flow using the shutoff valves can be damaging... any credence to that?


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## nokturnalkid (Apr 3, 2007)

As long as your plants are not bending in half and your fish being plastered to the walls of your tank, you should be fine. Just don't throttle the flow on your intake and your filter should be fine.


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## exv152 (Jun 8, 2009)

Restricting the output flow may cause some undue stress/damage to the impeller and motor down the road. I'm not an engineer but I'm sure it would be like letting your filter get clogged up with debris, and not cleaning it out regularly, which aside from causing nitrate and ammonia build-up, the clogging will have an effect on the longevity of the filter. Just my two cents.


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## thefisherman (Oct 15, 2011)

when you see your GBR on the surface with a boogie board then you have too much flow lol jk 

i use a 2217 to run my 20L. i don't use a flowbar, i use a flow pipe. 









now i have a nice clockwise current in my tank. is the flow too much?well yes it can be at first. but i find that as my filter matures (builds up with mulm) it eventually slows down to an acceptable level.

initially i adjusted the outflow valves of the speed connects... now i just have it on full open. the current is still firm but not to the point that its blowing scape out of the substrate.... my rainbowfish and amanos love surfing tho lol.

i think the larger tank and the fact ur using a 2215 is a good match where the flow will be more manageable. 


- thefisherman


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## thefisherman (Oct 15, 2011)

exv152 said:


> Restricting the output flow may cause some undue stress/damage to the impeller and motor. I'm not an engineer but I'm sure it would be like letting your filter get clogged up with debris and not cleaning it out regularly, which aside from cause nitrate and ammonia build-up, I'm sure the clogging has an effect on the longevity of the filter motor. It's safer for the equipment to increase the flow with various powerheads etc, and allow the hardware to function the way it was designed to, rather than do DIY modifications.


i initially felt the same way but disagree. i would be more concerned if the motor was belt driven... but its not. the ehiem filter head runs a magnetized ceramic impeller. basically it floats. sonif there was a restriction such as a clog, the piece could slip and not burn out the filter head. i guess ehiem knew what they were doing 

the only thing i would be concerned about is which side of the filter to restrict flow. i believe its safest to restrict on the outflow side (after the filter head). 



- thefisherman


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## NWA-Planted (Aug 27, 2011)

Little knowledge, learned in my sump building expeirence, as you throttle the outflow it does not harm your electric motor, it will actually cause them to use less current etc. NOW if the outflow is completely blocked then yes at that point damage will occur.

Also turnover and flow do not nescarily go hand in hand. Say you have a 500GPH pump, you could make the output a nozzle looking thing and really create a current, take that same outflow and hook up to say, a lily pipe, same GPH but not near the current in the tank


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## thefisherman (Oct 15, 2011)

NWA-Planted said:


> Little knowledge, learned in my sump building expeirence, as you throttle the outflow it does not harm your electric motor, it will actually cause them to use less current etc. NOW if the outflow is completely blocked then yes at that point damage will occur.
> 
> Also turnover and flow do not nescarily go hand in hand. Say you have a 500GPH pump, you could make the output a nozzle looking thing and really create a current, take that same outflow and hook up to say, a lily pipe, same GPH but not near the current in the tank


point taken... just to clarify i was referring specically to the Ehiem classic filter head/motor. i have no experience with the sump type motors you are regerring to. 



- thefisherman


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## xenxes (Dec 22, 2011)

No flow is too much flow! I like to see crashing waves in my tanks from 2 opposing filter heads set on max. Water stays clear even when I upset the dirt substrate into the water.

If your fauna isn't being blown across the tank sideways like in a hurricane and your plants aren't bent over/snapping/uprooting, then you're fine.


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## thefisherman (Oct 15, 2011)

xenxes said:


> No flow is too much flow! I like to see crashing waves in my tanks from 2 opposing filter heads set on max. Water stays clear even when I upset the dirt substrate into the water.
> 
> If your fauna isn't being blown across the tank sideways like in a hurricane and your plants aren't bent over/snapping/uprooting, then you're fine.


lol +1


- thefisherman


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## oldpunk78 (Nov 1, 2008)

I have a xp3 on my 60p. If you just look at the numbers, that works out to a turnover rate of about 20x per hour. (350gph/17g)

If I don't have a lot of plants in the tank, the filter blows the aquasoil around. Packed full of plants, it's perfect. The fish seem to enjoy the current too. There are plenty of places for them to get out of it though. I'd say they spend their time divided about half and half in and out of the flow heavy zones.

I will also note that the tank is super clean and I hardly ever have to clean the filter.


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## 150EH (Dec 6, 2004)

Restricting the flow will cause a load that is not designed into the filter, even though there are no parts touching is will create a load. I think it would be wiser to modify the spraybar angle or simple drill an extra hole to slow the flow a bit.


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## xenxes (Dec 22, 2011)

oldpunk78 said:


> I have a xp3 on my 60p. If you just look at the numbers, that works out to a turnover rate of about 20x per hour. (350gph/17g)
> 
> If I don't have a lot of plants in the tank, the filter blows the aquasoil around. Packed full of plants, it's perfect. The fish seem to enjoy the current too. There are plenty of places for them to get out of it though. I'd say they spend their time divided about half and half in and out of the flow heavy zones.
> 
> I will also note that the tank is super clean and I hardly ever have to clean the filter.


+1!

I have 17.65x in a 20 long, heavily planted. The fauna have plenty of places with no/minimal flow to hang out. During feeding I drop flakes into the current and they swim up in the water-threadmill if they want to eat (something McDonald's should implement).

Lots of plants + overfiltration = can keep more sensitive fauna healthy with low maintenance.

You can diffuse the flow more with a longer bar (not sure about your exact setup). Cutting a hole like 150EH suggested is also a good idea. If the canister still proves to be too much, you could always place 2 AC50's on either sides of the tank and aim them at each other 

*I read that the 2215 outputs 164 gph but is rated 93g??? Is that right? AC50 outputs 200gph. Are canisters different somehow?


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## JeffyFunk (Jan 10, 2011)

I think a lot of people here are using the terms "flow" and "force" interchangeably and they really shouldn't. 

Can a tank have too much "flow"? Probably not; In fact, most people do not have enough flow. 

Can a tank have too much "force"? Yes. As people have already stated, when the output of your canister filter is able to blow the plants over and send your fish flying all over your tank, then you have too much force. 

As an example, powerheads typically have a medium "flow" and a high "force"; The water from a powerhead exits the pump in a directional manner through a small opening. This increases the force that the water has. Most people who have planted tanks choose not to use powerheads, but rather choose water circulation devices like Hydor Koralia's or Ecotech Marine's. These water circulators have a high flow or turnover rate, but with much less force since the water being circulated is spread out over a greater area. 

How is flow and force different? Flow is the simply the turnover volume per time. Force is the energy (and direction) that the flow has coming out of the canister filter. If you want to maintain the flow of the canister filter but change the force of the water coming out, change the lily pipe that you use. This is explained in nice detail in the ADA catalogue and a recent issue of Aqua Journal (i can't remember which one - I think the January 2012 issue, but don't quote me on that). 

So in this case, if you want to decrease the force of the water exiting your canister filter, use a poppy glass lily pipe. The shape of the poppy glass filter pipe is designed to slow down the water as it exits the canister filter so you get a more gentle flow (as opposed to a strong, directional flow that you have now). 

p.s. I would guess that Eheim rates their canister filters not on the flow rate, but rather on the filtration capacity. In this case, while a Classic Eheim 2215 *might* be able to handle a 93 gallon tank, it would not be able to provide enough flow for a planted tank of a comparable size. I have a Classic Eheim 2215 on my 50 gallon tank and it's not powerful enough. (I do like the filter, but would rate the 2215 as being appropriate for a planted tank up to ~30 gallons or 2 feet in length. I plan on upgrading my filter to at least a 2217 or greater at some time.)


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## xenxes (Dec 22, 2011)

I see. So the 164 gph rate is accurate. Interesting, what else determines filtration capacity? I thought just surface area of biomedia + flow rate? I'm guessing difference between the 2215 and AC50 is the amount of the media? Both have similar flows 164/200.


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## DiabloCanine (Aug 26, 2005)

buffheman said:


> I just got an Eheim 2215 for my 29gal tall. Previously, I had an AC50... so you can imagine the difference is quite noticeable. I have the intake in the bottom right corner, and the spray bar on the back wall in the top left corner.
> 
> I originally had it pointed at the wall, but the flow still didn't seem great. So I pointed it out, and the it was nuts. Not crazy, like the plants weren't getting bent in half or anything, but the fish just looked like they were working really hard. So I just closed a little nozzle just a tad bit on the output hose, and I think I like it now. But two questions...
> 
> ...


You could put a "T" in the output line and run 2 spray bars or maybe install an external heater or inline CO2 reactor. Just some ideas. I do not think eheim intended that valve to be used in that manner tho.....DC


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