# Fluval C4?



## LeeAberdeen (Sep 4, 2014)

I'm thinking of getting one of these for my smaller tank, replacing the big sponge filter I've got in there, but I'm wondering if it's noisy or not? Anyone have one, or know?

I've never used a HOB filter before, they're not very popular in the UK for some reason, and I'm wondering if there's a reason for that? Both my tanks are in the front room, so I don't want anything making a racket. When I say 'racket', I have an FX6 on my big tank and the sort of noise from one of those is fine, just nothing above that.

Alternatively, any suggestions for another HOB filter, a big one with similar or greater capacity than the C4?


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## DJRansome (Oct 29, 2005)

HOB are noisier than canisters, especially if the waterline is not kept up to the lip of the return. The sponge filter must make some noise as well? Is this for the 75G? I have 2 canisters on each of mine.


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## LeeAberdeen (Sep 4, 2014)

DJRansome said:


> HOB are noisier than canisters, especially if the waterline is not kept up to the lip of the return. The sponge filter must make some noise as well? Is this for the 75G? I have 2 canisters on each of mine.


The sponge one is extremely silent, because it's attached to a Eheim 400 air pump which is incredibly quiet.

Yes, it's for the 75g. For some reason, after the sponge filter being there a couple of years, I've suddenly decided it takes up too much room and is ugly. Also, as a C4 is quite a powerful filter, I reckon it'll improve the water quality too.

I was thinking of putting a second canister on it, like yourself, but it would involve quite a major rearrangement of stuff under the tank to accommodate the pipes, so I'm seeing if I can get away with more filtering power with minimum disruption - just not at the expense of loads of noise...


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## DJRansome (Oct 29, 2005)

The noise from sponge filters is typically the bubbles. The noise from HOB is typically falling water.


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## LeeAberdeen (Sep 4, 2014)

If the noise is similar to that of the bubbles, I'm happy with that.

So, with a HOB, does the waterline always need to be kept near the return? What if it goes above?


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## Deeda (Oct 12, 2012)

The filter outflow is quieter if the waterline is closest to filter lip. The tank water line can go above the return from the filter as long as the filter lip is below the rim of the tank. HOB filter lips usually project below the tank rim.


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## Samadhikash (Jun 16, 2015)

I have two tanks with HOB's and old school box filters filled with floss (not a sponge filter, but they are air driven so the sound of constant air bubbles breaking the surface is the same). I've gotten so used to the sound of the air bubbles breaking that it generally doesn't even register anymore. I've always found it a pleasant sound. The HOB's are totally silent, making virtually no noise, so long as the water level is up to or above the lip of the return. If the water level drops below the lip of the return, it makes a distinctive waterfall-like sound. Personally, I don't care for it and it makes me crazy--I find it far more intrusive and jarring than the low rumble and roil of the air bubbles. Keeping the water line up, however, is simple and painless. But if you are one of those folks who run their tanks 2" below the trim line, it's definitely going to be noisy (not from the sound of the motor, but from the sound of water crashing into water). My 2 cents.


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## LeeAberdeen (Sep 4, 2014)

My tank's always topped up, but without going over the central brace that still puts the waterline 10cm or so below the rim. I'm hoping the lip of the return will come down lower than that, but it's difficult to tell from the pictures.


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## Samadhikash (Jun 16, 2015)

Not knowing the specifics of the C4 return or of your tank, I probably shouldn't have used an actual measurement. I didn't mean to cause you any stress on measurements and apologize if I did. If your water level is at or above the lip of the return, it will be quiet. If the water is below the return--such that the return water drops into the tank water as opposed to flowing into it--you'll get the waterfall sound. Disregard my use of an actual measurement, as it may not be meaningful in your situation in the same way it is in mine.


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