Fluval U3 Filter Change

[jetnett]

hello bought a second hand tank 3 weeks ago. very new to the tank world so got a few questions it came with fluval u3 filter. Today I changed the sponge and one of the carbon cartridge's as they where one year old. when can I change the second one ?
And I need to do a water change as my nitrite levels are at 0.25 mg/l. How long after cartridge and sponge change should I leave before a water change ?
Thank you jeanette

 

[Lunar Jetman]

Personally if it was me I'd throw the carbon away and replace it with another sponge. Then leave the sponges until they're falling apart, just rinsing them in tank water to clean them every few months or so.
 
My current filter, has sponges in it that are 7 years old and counting.
 
Re Nitrites, I'd carry out a 50% water change now and daily until you get those levels down.

 

[jetnett]

than

Personally if it was me I'd throw the carbon away and replace it with another sponge. Then leave the sponges until they're falling apart, just rinsing them in tank water to clean them every few months or so.
 
My current filter, has sponges in it that are 7 years old and counting.
 
Re Nitrites, I'd carry out a 50% water change now and daily until you get those levels down.

Thank you the sponges where so bad though so had to replace them but maybe I shouldn't change the cartdrige and sponge at the same time ?

 

[fluttermoth]

You shouldn't change more than one quarter of your filter media at any one time, and leave six to eight weeks before you replace any more.
 
Unless the sponge is actually disintegrating (which, in 30+ years of fishkeeping, I've never had happen...) you should not replace it.
 
I would also second LJs advice; dump the carbon cartridges and put an extra layer of sponge in there; they should fit in the slot perfectly well (they did in my U3 anyway!).

 

[jetnett]

ok

You shouldn't change more than one quarter of your filter media at any one time, and leave six to eight weeks before you replace any more.
 
Unless the sponge is actually disintegrating (which, in 30+ years of fishkeeping, I've never had happen...) you should not replace it.
 
I would also second LJs advice; dump the carbon cartridges and put an extra layer of sponge in there; they should fit in the slot perfectly well (they did in my U3 anyway!).

ok so would you advise me to put one of the old sponges back into the filter again ? just thought a sponge change could help me with my nitrite levels ?

 

[fluttermoth]

How long has the sponge been out of the filter, jetnett, and has it dried out? If it's only just been taken out, and is still damp, the bacteria may have survived and it would be worth putting it back in. If it's been more than a few days, and it's dry, then there's probably no point.
 
Changing filter media is the worst thing to do with any ammonia/nitrite spikes, as you want to keep as many of the bacteria as possible. Water changes are the way to go

 

[jetnett]

How long has the sponge been out of the filter, jetnett, and has it dried out? If it's only just been taken out, and is still damp, the bacteria may have survived and it would be worth putting it back in. If it's been more than a few days, and it's dry, then there's probably no point.
 
Changing filter media is the worst thing to do with any ammonia/nitrite spikes, as you want to keep as many of the bacteria as possible. Water changes are the way to go

ok the old sponges are back in I have carried out the water change and nitrite levels came down but a few days later back up again so I thought it could be the filter being dirty that is causing it will do another water change then
Thank you jeanette