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Fluval 306 flow stops after 6 hrs/overnight, noisy and mystery part

Emma_M

Seedling
Joined
7 Aug 2018
Messages
4
Location
Loveland, CO
Hi everyone,

I would like to hear your advice and thoughts about my Fluval 306 canister filter which is being incredibly frustrating! I just bought an established tank that came with the filter. I am a returning fish-keeper - I used to have them as a teenager but that's been a while. So, the filter works fine when first set up. The flow is great and creates quite a current in my tank (29 g, sand substrate, planted) but after a few hours it starts to reduce to the point where there is really only a small trickle coming out of the outlet after overnight. It also makes a gravelly noise. I have cleaned everything really well and multiple times and cleaned and greased (vaseline) the O-rings on the top and on the Aquastop inputs and also the impeller and shaft. I have also primed and shaken the pump to try to get any trapped air out. Note that there are NO air or microbubbles in the outlet water.

If I unplug, remove the Aquatstop completely, turn back on, the flow returns to normal BUT then reduces as described. Noise is still there.

Some things I have noticed:
- When I remove the Aquastop or move the lever a lot I do get a water droplet at the side on the grey... circle thing. Sorry, don't know the name but it's like the 'wheel' of the lever. Have attached a photo. It's beading because of vaseline on there. A few drops come out only when I move the grey aquastop lever and it's not much.
- The impeller cover appears to be warped. I don't know how much of an issue this will be
- Priming does NOT return flow to normal

ALSO on a side note, on first cleaning a little rubber stopper thing fell out! No idea where it goes. Any ideas? Attached is a photo of it alone with the flow

Hope to get some help! I am getting super frustrated with this thing!

Some photos attached: the 'mystery part', flow after 6 hrs/overnight, flow AFTER removing Aquastop and refitting (it then gradually returns to slow after 6 hours or so), leaking Aquastop
 

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I’ve not owned Fluval canister in ages but check the parts list to see if you can identify
- I can’t really judge size from photos, but confirm it’s not the impeller bushing

Parts List

I’d plan on replacing the impeller cover (as damaged) & impeller (they do wear), some shops may stock basic parts (impeller & impeller shaft/bushing)

Note that even low flow will keep your filter bacteria alive, if you’ve an air pump or any sort of internal powerhead this will help keep fish happy re water movement (oxygenation)
If lots of stock, also do daily water changes 25-50% to maintain good water quality, cooler water added to tank will have more dissolved oxygen
 
Thank you. I'm going to call in the morning. I'm not sure how much help I will get since I don't have proof of purchase :/

Thanks for tips RE keeping bacteria alive. I don't have too much stock right now and unplugging and reconnecting the aquastop seems to fix the problem for a little while.
 
Update: they have agreed to send me the two replacement parts (impeller cover and Aquastop) so I will update when those arrive and see if it fixes the problem
 
Is it possible the mystery part is one of the rubber feet from the canister base?
 
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