# Chopped coarse filter foam as media



## bigmatt (24 Mar 2010)

Hey all,
As a newcomer to the site i've learnt loads about vairous things, but the thing i'm finding really interesting is the range of views and options regarding filter media.  I didn't really want to start a new thread but i couldn't find this quesiton answered anywhere else!
I know there is a lot of love for sintered glass but (in keeping with the rest of my posts) i'm a bit of a cheapskate and can't run to this at the mo   However i do have tons of filter foam after buying one of the packs from MA a while back that's intended for pond pumps and consists of three different grades of filter sponge in massive sheets(i think 1m x 75cm) for Â£12 - bargain (and a top tip for anyone looking to cut costs  - saves a fortune and all you need are scissors and some patience to make loads of filter pads)!    I presently run ceramic rings (bottom tray), coarse filter foam pads(middle) and more coarse foam and floss (top) in my filter. What do members think about using chopped coarse filter  foam loosely packed in the middle tray instead of the pads?  my thinking is that is should enhance random flow creating good particulate trapping as well as providing a massive surface area for bacteria, coupled with minimal mechanical resistance to flow improving filter turnover.  
I'm going to give it a go so i'll let you know how i get on but i was wondering if anyone has tried it and/or if i'm missing something really obvious!
Cheers folks!
Matt


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## Ed Seeley (24 Mar 2010)

Chopped up filter mat will be just as good as ordinary filter mat biologically.  However it will almost certainly give you less volume of media as there will be spaces between the pieces of foam.  But this probably won't matter in reality as we usually totally overspec our filters and have way too much filter media anyway.

I still like sintered glass though and even use a similar ceramic media on one of my ponds.  I think it offers more advantages than just increased surface area.  If you want to save money you might want to look at Alfagrog as a possible replacement - I am going to try it in my pond and see how it compares to the ceramic media.


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## ceg4048 (24 Mar 2010)

Check this thread and the links it contains Filter Media
Some very interesting surface area v cost comparisons.

Cheers,


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## bigmatt (25 Mar 2010)

ceg4048 - you are the man as always! That link is fascinating - if i get time it might be worth doing a UK version (in metric with UK costings!) and i'll post it in a clearly marked thread.
Guess i'll be buying some activated charcoal then!  Seems the best trade-off between massive surface area and low cost.  I guess in this instance the absorbency qualities of the media (i work as a Paramedic so have a grasp on the medical uses of acitvated carbon, and i guess it's just the same in a filter) are secondary to it's surface area, therefore it can stay in the filter indefinitely (with regular cleaning of course).
I might also have to do some flow comparisons between filter foam pads and the same volume of media chopped to see which gives best overall flow.  
I'm going to be busy!
Cheers again for your thoughts folks
Matt


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## dw1305 (25 Mar 2010)

Hi all,
I like all of ceramic, sintered glass, pan scrubbers, charcoal, alfagrog and chopped sponge, it's like Ed and Clive say it doesn't really matter what you use as long as it has reasonable surface area for bacterial colonisation, often the problems with biological filtration arise because the media impedes the water flow through the filter and the water becomes de-oxygenated whilst it is still in the filter, although this tends to be less of a problem for planted aquariums than un-planted ones. I've found (from our work on landfill leachates, and talking to  other aquarists), that  the amount of oxygen required by the nitrogen cycle (and "ordinary" heterotrophic bacteria in decomposition) is often grossly under-estimated. 

I'm a cheap skate to and I usually buy either the dimpled sheets you have or the 12" x 4" x 4" "Kettering Koi" sponges. I prefer the coarse ppi10 or medium ppi20 sponges, a great advantage of them over narly all other media is that they are very easy to clean. If I had a denser ppi30 sponge I might chop it into bits, otherwise I'd just cut a pad to shape.  The potential problem with the denser sponges is that are efficient mechanical filters, which tends to lead to clogging, reduced water flow and oxygen depletion, negating their potentially larger surface area for bacterial colonisation. If you use the charcoal you will probably be best putting it in a bag, as otherwise it tends to "escape" over time.

cheers Darrel


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## bigmatt (25 Mar 2010)

Thanks Darrel - you're quite right about oxygen and the Nitrogen cycle!  I hadn't even realised it was a required component until using this forum - i'd assumed it was an anaerobic process.  
If using Ac. Carbon in a bag am i best using a foam layer as a "pre filter"?  I've had a look at some media bags and they all use quite fine mesh, so i'm concerned about the mesh becoming clogged and impeding flow.  Or could i "sandwich" the carbon between 2 coarse foam layers without a bag to stop it escaping without compromising flow too much?
On a slight aside do think high filter flow is beneficial not just for distribution of nutrients but also because of this oxygen factor in the nitrogen cycle.  My (probably quite skewed!) logic works like this ... Improving flow in the tank (be it high filter turnover or use of additional circulation pumps) increases dissolved oxygen as more surface area is presented for gas exchange in the aquarium.  In planted tanks this turnover is typically massive and, i would imagine, leads to higher oxygen content in the water that is returned to the filter.  This in turn is advantageous to the nitrgen cycle in the filter, leading to higher densities of denitrying bacteria.  In turn they reduce ammonia etc. to much lower levels, returning cleaner water to the aquarium and reducing the likelihood of algae.  
I know the picture is very complex with many factors coming into play (including typically lower livestock levels in planted aquaria), but this seems to be a logical conclusion adding further weight to the concept of using overrated filters in ALL tanks with highest surface area possible media.  
Thanks again,
Matt


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## dw1305 (25 Mar 2010)

Hi Matt,
The conversion of NO3 to N2 is anaerobic,  but the rest is quite an oxygen and energy intensive process. Your flow assumption is pretty much right, have a look here http://www.advancedaquarist.com/2007/1/aafeature/. 

The main reason planted aquaria usually have better water quality than un-planted ones is simply the actively growing plants, at it's most fundamental they not only produce O2 when they are photosynthesising, but they also preferentially take up ammonia, this then doesn't enter the nitrogen cycle and therefore doesn't use up the 2 molecules of oxygen that each molecule of ammonia (NH3) would during it's conversion to nitrite (NO2) and eventually nitrate (NO3).  

The foam is usually as a mechanical pre-filter and as long as you can maintain flow through the filter, it doesn't really matter what order you have the elements in. I'm not big on the mechanics of canister filters (I liked ceg4048 description "No matter what, a filter is a bucket with a pump" from http://ukaps.org/forum/viewtopic.php?f=38&t=10235&start=0 ), so I'll let someone who knows what they are talking about tell you more about the order of the elements for easy of cleaning etc.

cheers Darrel


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## ceg4048 (26 Mar 2010)

Hi guys,
           For the most part, a lot of the reasoning for the sequence of canister filter element placement (at least in high end filters) is to protect the high surface area biomedia from clogging with detritus, even though biological filtration occurs on all the elements. So, typically you'll have one or two layers of coarse "pre-filter" foam to pull out the larger particles, then you'll often see the next stage filled with noodle looking cylinders. the intent, believe it or not, is to slow the flow by presenting a high friction cross section. As the flow slows, dirt particles that were small enough to make it through the coarse filter pads will fall out of suspension due to the slowed flow and will get trapped in between the noodles. That's why the noodles are often referred to as "mechanical" filtration. The subsequent stages are then typically where the high surface area biomedia or chemical media (such as carbon, zeolite, purigen and so forth are supposed to be. This theoretically lowers the rate at which the porous biomedia get clogged and enables you to simply change out the "pre-filters" and wash/replace them. Clogged biomedia have less surface area available for bacteria to adhere, or at least so the story goes.

If you want to improve your filter flow, you can simply delete the noodles and just add more foam. Those noodles quite literally are a major drag. Fluval make a combination carbon/zeolite mixture and it's best to use the activated carbon as free particles as opposed to using a bag. Avoid the charcoal as this is messy.

High flow in-and-of itself does not necessarily increase dissolved oxygen content. The oxygen must be produced somewhere, either by gas exchange at the surface or by ejection into the water column by photosynthesis. High flow however will carry and distribute the dissolved gasses better. So it will carry CO2 to the plant surfaces more effectively (and therefore indirectly increase oxygen production by the leaves) and high flow will remove areas of stagnant water and waste products away from the plant thereby improving nutrient and gas uptake by the leaves and so indirectly improve oxygen production. Naturally, as you say, this flow will then carry the improved oxygen production to the bacterial colonies more effectively so that they can take advantage of the extra living space of the biomedia by increasing their population densities. Fauna benefit directly by having higher oxygen rates delivered to their gills.

Cheers,


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