Replacing Fluval U2 filter components

[Fox46]

I’m down to one tank (from 3) and using up redundant equipment from those tanks. So it’s a 132l tank (including substrate and a moderate amount of tank furniture) in which I have a U2 filter, (capability 110l) supplemented by 2 small 25l spray bar filters, one of which is for surface agitation and to supplement the capability of the U2, and the other a stand-by primed emergency filter for a 25l hospital tank if necessary.

It's been a good while since I replaced any components in the main U2 filter and am now about to replace the poly carb pads, the sponge filters and the biomax. (All of these components get cleaned monthly, obviously in tank water.)

Would there be a risk of the cycle crashing if I replaced all three components of the U2 filter at the same time, relying on the 2x 25l filters to maintain the cycle during the ‘seeding’ process, or is there an order and timescale in which to tackle replacement of the components individually.

Also, the U2 filter is about 5 years old now. Anyone have experience of the likely life-time of this filter?

 

[TNG]

Not many members use the Fluval U series internal filters, so you aren’t likely to get many responses.

I have a U3, the next size up from yours, but only used it for around 18 months or so. I had to clean it every week so is a bit of a chore. I replaced it with a much simpler Eheim Pickup 160 which uses a simple sponge.

Fluval tells you to replace the biomax and sponges every 6 months but this is not necessary. You can keep using them until they fall to pieces. The sponges and biomax will last for years. The carbon (poly carb pads) is a different story as carbon loses its effectiveness after a few weeks, but carbon is not really necessary so you can simply remove them after a few weeks and not replace them.

Whether replacing all the components at once would cause the cycle to crash depends on what you have in your tank. I have rocks, sand, driftwood and plants in my tank, and the filters are there to oxygenate water and remove fine particles from the water. I have a larger filter which is on only during the day, and a very small and less noisy filter which is on at night time.

Some say turning a filter off half the time would kills the bacteria, while others say the rock, sand, etc. would not provide much bacteria. If these are both is true, my fish would all be dead. I’d love to be able to test how much bacteria can be found on rocks, substrate and filter, and if turning the filter off half the time would really kill the bacteria.

The component susceptible to failure is the impeller, but the U series look well-made and the impeller can be replaced.

 

[Fox46]

Not many members use the Fluval U series internal filters, so you aren’t likely to get many responses.

I have a U3, the next size up from yours, but only used it for around 18 months or so. I had to clean it every week so is a bit of a chore. I replaced it with a much simpler Eheim Pickup 160 which uses a simple sponge.

Fluval tells you to replace the biomax and sponges every 6 months but this is not necessary. You can keep using them until they fall to pieces. The sponges and biomax will last for years. The carbon (poly carb pads) is a different story as carbon loses its effectiveness after a few weeks, but carbon is not really necessary so you can simply remove them after a few weeks and not replace them.

Whether replacing all the components at once would cause the cycle to crash depends on what you have in your tank. I have rocks, sand, driftwood and plants in my tank, and the filters are there to oxygenate water and remove fine particles from the water. I have a larger filter which is on only during the day, and a very small and less noisy filter which is on at night time.

Some say turning a filter off half the time would kills the bacteria, while others say the rock, sand, etc. would not provide much bacteria. If these are both is true, my fish would all be dead. I’d love to be able to test how much bacteria can be found on rocks, substrate and filter, and if turning the filter off half the time would really kill the bacteria.

The component susceptible to failure is the impeller, but the U series look well-made and the impeller can be replaced.

Thanks for responding. I've never had the need to clean the filters weekly, I find monthly is adequate but I've tended to keep the population low. That's changing now, as I imported some livebearers who seem to do nothing but fornicate so I'm having to sharpen up my act a bit. I have sand, rocks, driftwood, live plants and some artificial in the tank. I think maybe I'll start by changing the poly carb filters, then (as I've already ordered them) change one sponge at a time over an interval. The U2 is working well, but has a tendency to need a bit of manual assistance to restart after water changes, hence my question. I'll take a look at the Epheim in readiness for the time when the usual jiggery pokery fails to get the U2 running. Thanks for the info.

 

[MattW]

I recently added a U3 to my 60L. It's overkill for the tank, but I was having issues with mulm buildup. I decided to ditch the carbon and poly pads and just use sponge and the bio media in the centre compartment. I went for the coarse sponge on the outside with a finer sponge behind that. I still haven't cleaned it yet, about a month after I added it to the tank.

 

[Fox46]

I recently added a U3 to my 60L. It's overkill for the tank, but I was having issues with mulm buildup. I decided to ditch the carbon and poly pads and just use sponge and the bio media in the centre compartment. I went for the coarse sponge on the outside with a finer sponge behind that. I still haven't cleaned it yet, about a month after I added it to the tank.
View attachment 369712

What made you decide to ditch the poly carb pads?

 

[MattW]

Main reason is that they get clogged quicker than a sponge. Of course, they filter out finer particles, but my water has always been clear so I don't see the need. Secondly, I stopped using carbon a while back. I sometimes dose ferts, so I don't want the carbon absorbing anything intended for the plants. My U3 is in a heavily planted tank, so it needs access to as much plant food as possible

 

[Fox46]

Main reason is that they get clogged quicker than a sponge. Of course, they filter out finer particles, but my water has always been clear so I don't see the need. Secondly, I stopped using carbon a while back. I sometimes dose ferts, so I don't want the carbon absorbing anything intended for the plants. My U3 is in a heavily planted tank, so it needs access to as much plant food as possible

View attachment 369765

Thanks, looking good.