Fluval U4 - How often should you change the sponges?

JChops

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Hi everyone,

Apologies if this isn't the right forum for this. I've recently purchased a Fluval Roma 200 which has a Fluval U4 internal filter. The thing I'm unsure about is how often to change the sponges in the filter cartridges. There's a white and a black sponge either side of the Biomax, so I assume I'd need this and this? I was thinking of doing a water change approx every 5 weeks and replacing one, then 5 weeks later replacing the other one. Any feedback on this would be great :) Thanks!
 

kwi

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Only when they fall apart, those both contain carbon which isn't really needed so can be replaced with just sponge.
The filter media is where most of your nitrifying bacteria live and it's not a great idea to get rid of a chunk of those.
Just swill them out in tank water every now and then to remove the poop and other solid waste.

Also 5 weeks between water changes is very long. I can get away with fortnightly but still do weekly.
 

Dajuyu

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Am using Fluval C4 sponges and C nodes ... well its unlike Canister filter where you cant see whats going on inside.
So when I see the sponges become black the day that I am not doing WC I will swirl the sponge with the water from the tank .
To keep it not that black anyways ...
 

cdelly

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i replace them when they are looking a bit worn

you are right in changing just 1 at once, keeps some bacteria in the filter to populate the new sponge.

also you dont need to buy fluval sponges, you can buy other makes or replace with filterfloss(would need changing more often) or just sponge
 

AbbeysDad

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Unless you have LOTs of plants and very FEW fish, I feel 5 weeks is way to long. "There's no such thing as too much fresh, clean water!". I do 50% weekly water changes and with heavily stocked grow out tanks I do 50% twice per week.
Filters should be serviced at least weekly (get the crud out of the system) and sponges last nearly forever until as @kwi noted, until they practically fall apart.
 

QiQi

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Don't forget that you need to clean the sponges in old tank water, so you don't kill the beneficial bacteria. Easiest way to do it is when you do your weekly water change. Just squish the sponges several times in that water.
 

Dajuyu

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Unless you have LOTs of plants and very FEW fish, I feel 5 weeks is way to long. "There's no such thing as too much fresh, clean water!". I do 50% weekly water changes and with heavily stocked grow out tanks I do 50% twice per week.
Filters should be serviced at least weekly (get the crud out of the system) and sponges last nearly forever until as @kwi noted, until they practically fall apart.
Now thats more like it ... I did twice a week WC and once a week filters cleaning taking turns ... I thought I am the only one who is frantic about WC
 

Essjay

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A Fluval U4 comes with:
a box containing biomax (ceramic rings)
2 foam pads
2 poly/carbon cartridges


Of these, the biomax and foams do not need to be changes till they crumble/fall apart.
The poly/carbon cartridges can be replaced by filter floss as mentioned above. This does not wash well, and can be replaced when it does into holes. Carbon is not needed.
 

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