# Sponge Filters.... effective?



## beachtan (Sep 25, 2008)

How effective are sponge filters compared to HOB's? Not so concerned with appearance...


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## clgkag (Mar 22, 2008)

Very effective at biological filtration, but may not keep up on the mechanical.


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## aquariam (Feb 11, 2010)

Significantly better biofiltration than a HOB. As mentioned the mechanical is not spectacular. You really need to keep on top of it and vaccuum debris manually. If you were to use the two together you could have the benefits of both.

The nicest fish I've ever seen were bred/breeding in sponge filter tanks. I know someone who runs a 90 gallon exclusively on (way too many to look attractive) sponge filters. It looks awful but the fish are stunning.

If you want a HOB just for mechanical you want something with a high flow rate across a smaller area. Something with a filter pad is often more effective for that, like a whisper. I'm not a fan otherwise but it works.


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## BillD (May 17, 2005)

They don't offer significantly better bio filtration than a HOB, unless they offer significantly larger in surface area than the HOB. They do a good job of removing fine particles and heavier bits tend to congregate at the base, making it easy to vacuum debris during water changes. You can look at it this way. For the price of a name brand cannister to filter a 75, you can buy a 75 gallon tank, 2 #5 Hydrosponges, a heater, and an air pump.


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## smellsfishy1 (May 29, 2008)

An HOB can be setup with different types of media and customized many ways thus making a better choice over sponge filters.
It really allows you to distribute the filtering responsibilities of each medium.

Mechanically and biologically the HOB is superior to the sponge filter if maintained and setup properly.
A sponge filter has no chemical filtering capability, if you should decide to want this at any given point in time.

For simplicity the sponge filter is just fine.
I like sponge filters because I can hook up one pump and filter multiple tanks.
Sponge filters are ideal for fry and grow out setups.


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## aquariam (Feb 11, 2010)

BillD said:


> They don't offer significantly better bio filtration than a HOB,


Um, yes they do.


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## BillD (May 17, 2005)

aquariam said:


> BillD said:
> 
> 
> > They don't offer significantly better bio filtration than a HOB,
> ...


You are basing this on what?
If they have the same bio media surface area, they will be the same. Regardless, they are an inexpensive, efficient form of filtration.


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## aquariam (Feb 11, 2010)

BillD said:


> aquariam said:
> 
> 
> > BillD said:
> ...


It's not just your surface area, it's how you flow water through it. The speed, distribution, and contact time of the flow make a difference. Jm2c


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## pistolpete (Dec 28, 2009)

reading various sources over the years I have formed the impression that faster flow rates are better for bacteria. Apparently the densest concentrations of bacteria live in the intake tubes of a HOB, that's why they always look brownish. The trouble is there just isn't enough surface area in the tubes.

anyway what I'm getting at is that a faster flow filter will be a bit better on the biological side if the surface area exposed to water flow of both filters is the same. It's the fact that sponge filters usually have a lot more surface area than a small HOB that makes them effective.

What seals the deal for me is the noise of an air pump + bubbles. Can't stand the racket, so I just stuff my HOB's with foam only.


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## kmuda (Nov 27, 2009)

pistolpete said:


> reading various sources over the years I have formed the impression that faster flow rates are better for bacteria. Apparently the densest concentrations of bacteria live in the intake tubes of a HOB, that's why they always look brownish. The trouble is there just isn't enough surface area in the tubes


There are actually physical dynamics in play and, as it relates to biological filtration, higher flow can actually be detrimental.

A good article that discusses this in depth can be found here, specifically the section located a little more than halfway down titled "Dynamics of Aquarium Filtration":
http://www.seachem.com/Library/Articles ... ration.pdf

In a nutshell, what this article tells us is what we already know. HOB's are better at mechanical filtration, canisters are better at biological filtration. Mechanical filtration improves with higher flow rates and biofiltration has a point where flow rate becomes detrimental. And.... Canister filters are much more efficient than HOB filters.

Not that this has a lot to do with stand alone Sponge filters themselves, more to do with flow rates, but many of the same dynamics apply.

For biofiltration... on a 4" sponge, I would consider optimal flow rate between 30gph and 50gph. As sponge size decreases, so would the optimal flow rate.

As for "bacteria in the filter tubes", absolutely. Although, I would not consider the tubes as containing the "densest concentration" for the simple reason you described, an absence of surface area. If tallying up the total colonies of bacteria, those found in the filter tubes would be a minor percentage of the bacteria in the tank. But the filter tubes will certainly be an area where the greatest concentration of the compounds the bacteria are consuming will be located. Where ever these compounds are, there will be bacteria.


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## beachtan (Sep 25, 2008)

great posts everyone! Thanks!!

Now I've been cleaning my uplift tubes diligently since, although I dont mind the look of the sponge, I do mind the grubby look of a dirty uplift tube!! So I need to leave them dirty, your telling me, huh....


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## Rick_Lindsey (Aug 26, 2002)

I wouldn't worry about it, beachtan. If you've got enough bacteria, then you've got enough bacteria. Unless it causes a mini-cycle every time you do it, if you like the look of clean tubes then keep 'em clean!

-Rick (the armchair aquarist)


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## LSBoost (Jan 21, 2010)

beachtan said:


> great posts everyone! Thanks!!
> 
> Now I've been cleaning my uplift tubes diligently since, although I dont mind the look of the sponge, I do mind the grubby look of a dirty uplift tube!! So I need to leave them dirty, your telling me, huh....


Here's an idea, what if you paint your uplift tube black and never clean it again!. I never clean any of my filter tubes and it never clogs.


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## alexlee04 (Jul 19, 2009)

since we are on the topic of lift tubes. I have seen many experienced dealers who don't use lift tubes on their sponge filters. I was just wondering if there is a reason for this or if its just for looks?


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## BillD (May 17, 2005)

I see this all the time too. Not using a lift tube will seriously reduce the water flowing through the filter. The longer the tube the higher the flow. Back in the old days we would add a length of tube to a box filter to increase it 's flow.


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## alexlee04 (Jul 19, 2009)

Hummm so maybe by lowering the flow rate you increase the effectiveness of the bio filtration? :-? Does anyone here use your sponge filters without lift tubes? If so please explain this to me. Thanks!


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## nick a (Apr 9, 2004)

I'm curious about this "The longer the tube the higher the flow.", BillD
Not disputing it...just curious as to the physics behind it.

Let's say we have 10 bubbles with a surface area of 'x' rising and moving 'y' amount of water with them...how can the DISTANCE traveled increase the flow rate?


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## BillD (May 17, 2005)

The bubbles don't move the water, gravity does. When you add a stream of air into water column, you lessen it's density. the greater the difference between the density in the column, and where the water enters it, the greater the effect of the water pressure. So, the greater the length of the tube, the greater the difference between the two pressures.


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## kmuda (Nov 27, 2009)

alexlee04 said:


> Hummm so maybe by lowering the flow rate you increase the effectiveness of the bio filtration? :-? !


It's not that simple as there are variables in play, chiefly media depth and width (which combined equal media volume). The higher the media bed volume, the higher the flow rate can be. In general, most canisters optimize their flow rate based upon these factors. It's what makes Eheim... Eheim. Eheim canisters are engineered with these factors in mind. It is also one of things that turns me off about Fluval, as these factors are totally outside of consideration (except, possibly, for the overpriced G-Series). Fluval generally takes the Tim Allen approach (more power), even though more power may not provide any more benefit than a resulting artificial nad inflating testosterone boost. Eheim sometimes takes a hit for their lower flow rates when compared to other filters. But other filters are not necessarily engineered with an optimal flow rate based upon media volume. Give Eheim credit, they've never been coerced into the Tim Allen approach, which is as much marketing as anything.

As for most cartridge type HOB filters, anything over 60GPH is actually detrimental to biofiltration, but beneficial to mechanical filtration. Again, because the media depth is extremely limited. The filter width (in the cartridge) is substantial, which is good for mechanical (as is higher flow rate), but an absence of media depth combined with high flow are not conducive to biofiltration.

The only two HOBs that overcome these limitations in dynamics are the AquaClear line and the Penguin/Emperor line. The Aquaclears do it by simulating, in a small fashion, canister filters... in that they increase the media depth. However, the media volume is still tiny compared to a decent canister and 500GPH (on an AC110) is major overkill, providing no more benefit really than a good powerhead with a sponge prefilter on it. The Penguin/Emperor line, on the other hand, over comes limitations in dynamics via Biowheels and use of Biowheels allows for full utilization of 400GPH (on an Emperor 400) for biofiltration. But the Penguin/Emperor lines are inferior to the Aquaclears when it comes to mechanical. So it really depends on what your needs are.


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