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Discussion Starter · #1 ·
My Eheim Experience 350 seems to vary in output during the day. I don’t like this unstable flow as I want to keep my co2 and flow stable during the day.
I observed that the surface ripple changes between ‘normal’ and very intense (the surface ripple becomes much much stronger not a little bit).

I would like to hear your opinions about possible variables that could have effect on the output of the filter. So I have a 'complete' list to troubleshoot.

I troubleshooted a little bit and did the following:

* Make sure the inflow isn’t restricted with leaves.
* Changed the amount my inflow skimmer will suck in so it doesn't suck a lot of air in. When I move the filter a bit I don't hear any air that escapes the filter.
* Cleaned the filtermedia
* Cleaned the Impeller
* Cleaned the filter hoses
* Changed the O-rings for the filter media baskets
* I don't run my filter on Full output it's too much. Around half open. But according to Eheim there should be no problem tweaking the build in valves as long it is on the output. The inflow valve is fully open.

The filter is around 3,5 years old. Could the Impeller be damaged and cause this problem? Should I replace it? Any other parts that could have effect on my problem?

The hoses aren't extremely 'long' just next to the tank.

As I can't hear any air escaping when moving the filter a bit can I assume to rule out that the connections of the hoses, inflow, outflow and 90 degree pvc parts don't suck in any air? I don't have any leaks? I did change the hoses once both advertised as 16/22 however the new ones are going a little bit easier on the connections. No leaks however and I don't hear any air escaping when I tilt the filter.

Let me know what you think!
 

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Discussion Starter · #3 ·
The flow goes up and down during the same day? assuming you don't have anything blocking the flow and then getting removed, it's almost certainly a motor starting to go bad.
Yep sometimes even multiple times a day it changes. In your opinion pointless to swap out the impeller I assume?
 

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Yep sometimes even multiple times a day it changes. In your opinion pointless to swap out the impeller I assume?
Yes, there is no reason the flow should by yoyoing from an impeller issue. If its clogged or broken you would expect it to decrease and remain steady.
 

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A couple other things to check are that the white fine pad is not under the handle of the top media basket but on top of the media basket and also that the input connector piece on the underside of the filter head is in position correctly so that it inserts into the top media tray opening.
 
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Discussion Starter · #6 ·
A couple other things to check are that the white fine pad is not under the handle of the top media basket but on top of the media basket and also that the input connector piece on the underside of the filter head is in position correctly so that it inserts into the top media tray opening.

Thank you yes unfortunately this is already done the 'correct' way..
 

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Considering how the "Motor" is made, I do not find it likely for it to be going bad and then working again as it is simply a coil of wire embedded in epoxy which forms a magnetic field to turn the impeller. If the wire in epoxy goes bad, it is not likely to go closed again as there will be a pretty big arc. and fry anything in the area too much to work again.
I find the most likely cause is not getting the air fully out of the impeller area or there is air leaking in at some point as the impeller will only pump water and not air very well at all. Slow and jerky flow as more more water or air gets to the impeller is very common on any canister.
I would first look at how the outflow looks. Is it pushing a lot of bubbles at times but not at other times? That tells you it is getting air and spitting it out as the flow varies. Perhaps try slowly tilting and rotating the canister so that any air pocket near the impeller will go up, find the opening and you will see it go out the outflow as a burst of bubbles?
But then there are other things like hard media which can get in places like the outflow where we can't see it but one of the Barrel shaped hard media in the output can be hard to spot and roll in and out to change flow.
Floating floss, etc. is a definite thing to check, even to removing that layer for a test.
 

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Discussion Starter · #8 ·
Considering how the "Motor" is made, I do not find it likely for it to be going bad and then working again as it is simply a coil of wire embedded in epoxy which forms a magnetic field to turn the impeller. If the wire in epoxy goes bad, it is not likely to go closed again as there will be a pretty big arc. and fry anything in the area too much to work again.
I find the most likely cause is not getting the air fully out of the impeller area or there is air leaking in at some point as the impeller will only pump water and not air very well at all. Slow and jerky flow as more more water or air gets to the impeller is very common on any canister.
I would first look at how the outflow looks. Is it pushing a lot of bubbles at times but not at other times? That tells you it is getting air and spitting it out as the flow varies. Perhaps try slowly tilting and rotating the canister so that any air pocket near the impeller will go up, find the opening and you will see it go out the outflow as a burst of bubbles?
But then there are other things like hard media which can get in places like the outflow where we can't see it but one of the Barrel shaped hard media in the output can be hard to spot and roll in and out to change flow.
Floating floss, etc. is a definite thing to check, even to removing that layer for a test.

Yeah I tried this several times a day with tilting the filter slightly but usually I don't hear any filter burps so it doesn't seem to be an air issue? Or could it still be after doing this tests?


I will check the outflow however I also use an atomizer so hopefully I can see it.



No filter floss in the filter currently.


I'm at a point of changing the filter... but if I could still fix it that would be great.
 

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Pretty expensive items to replace if not needed and they are often so reliable that I go a long way before saying they are bad.
A real pain to do just for testing but if you unload the media canister almost completely and run for an hour to see full flow, it might tell you there is an internal problem?
Do you have the normal Eheim green tubing that you can see through so that bubbles would show there as you tilt and rotate it?
The bubbles I might expect if that were the problem would not be small as they come out but great big ones that burp and make all kinds of noise when the come out in the tank if the end is under water. I feel if it is big enough to bother flow, the bubbles will be the big noisy thing like using your head to blow out bubbles when swimming!
The place where I found I had dropped a small bit of the hard media was in the small plastic elbow at the bottom of the canister where I overlooked it for a long time. Finally when almost done looking and turning the empty can around and holding up to the light to look for cracks, the little devil dropped out!
 
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