The Aquatic Gazette

Eheim Liberty 100/2040

In Filtration on May 5, 2011 at 10:37

The Eheim Liberty is the hang-on filter series for this reputable filter company. In nano tanks when the need of filtration media quantity is not that great, these filters are popular as they are simple to set-up, they provide an ease to maintenance, they are cheaper compared to cannister filters and they are less of an eyesore compared to internal filters.

Eheim Liberty 100/2040

Technical Specifications
Model: 100 / 2040 (depending on your region)
Approx Max Aquarium Size: 75 litres
Approx Pump Output: 150 to 380 litres per hour
Power Consumption: 2.5 Watts
Available Filtration Volume: 600ml
Approx Filter Volume: 240 litres
Dimensions: 180mm x 105mm x 135mm

The Liberty 100/2040 is the smallest hang-on filter in the series. Build quality is solid and excellent, one of the best constructed hang-on filter in the market. Every part of the filter speaks of quality, and you do feel a sense of pride when assembling it. The red flow switch is large and has nice resistance to it, which makes for a precise control of your filter’s flow rate. The cover of the media compartment doubles up as water catchment when removing your filter media for cleaning. Filter media cartridges are similarly well constructed and their black handles makes insertion and removal a painless affair. Everything feels snug and tight in this filter, there are no loose bits or poorly machined parts.

How great a filter performs is dependent on two fundamentals;
1. How the flow of water has been designed
2. How well the filter media performs

With cannister filters, it is common to use your own preferred media, you are not restricted to the cannister company’s media. For hang-on filters, it is another story altogether. Hang-on filters are much smaller than cannister filters and their media are specially made to fit their interiors. Using company’s A media for company’s B hang-on filter is not always going to work. Even if you could fit it in, it is not going to fit tightly and you do not want any flow bypassing your media through the cracks. Modifications are possible and can be found on the numerous aquatic forums, but it is not going to be everyone’s cup of tea.

Eheim Liberty 100/2040 comes default with a blue sponge cartridge that is meant for general filtration, in other words, it is a mechanical and biological filter sponge. Again, the quality of the Liberty series translates to a filter sponge that is very well made, we can easily foresee a decade of use without any problems. Performance wise though, it is slightly disappointing. The blue sponge cartridge reminds us of Eheim’s blue filter pads from their cannister filter range. These blue filter pads are meant for mechanical filtration, trapping the bigger amounts of dirt so as to prevent your biological media from getting bogged down. It may be because of their similarity that the blue sponge cartridge works exceedingly well as a mechanical media, but in doing so, it prevents effective water flow throughout the blue filter sponge as the front wall clogs up quickly because of the small surface footprint. If the blue sponge cartridge is not cleaned on a weekly basis, quite a bit of water flow will bypass the sponge and flow over it instead.

blue sponge cartridge

However, the biggest issue we have with the blue sponge cartridge, is its inability to polish the aquarium water as it leaves the filter. Most competing brands will incorporate a fine filter wool media in their filter and this filter wool will trap minute dirt. Because the blue filter sponge is not fine enough to trap these minute dirt, you will see them flowing around your aquarium.

blue sponge cartridge | close up

Instead of using the blue filter sponge, there is the choice of purchasing the green sponge cartridge together with the carbon cartridge. The green sponge cartridge is touted to be a superior, biological friendly media and the carbon sponge is your usual chemical filtration media.

The green sponge cartridge has a smaller cross section than the blue sponge cartridge, as such, more surface area should be available for beneficial bacteria cultivation. We can see the smaller cross section as being the reason why the green sponge cartridge will be more effective for biological filtration. But in overall sponge size, it is only about a third as thick, as the blue sponge cartridge. So unless the green sponge cartridge’s biological effectiveness is more than 3 times that of the blue sponge cartridge, the superior biological claim is not really true. We wish Eheim will release more technical and research data on all their filtration products, like Seachem does. This will enable us to make filtration decisions based on hard facts.

green sponge cartridge | close up

blue & green sponge | size comparison

The major difference the green sponge cartridge has, is in water flow. The blue sponge is designed to have all flow passing through it while the green sponge is designed to have some flow pass over it. The reason for such a design is that water that comes into contact with the green sponge and then pass over it has more contact time with the biological bacteria than if passing through it. To achieve this, the green sponge is lower in height when compared to the blue sponge, encouraging water to pass above it instead of going through it, as there is less flow resistance in doing so. How much of an advantage is this, we will never really know unless an extensive test is done in a controlled environment.

green filter sponge | carbon sponge

When using the green sponge cartridge, an activated carbon cartridge is also to be used, using a carbon cartridge brings chemical filtration to the fore. Chemical filtration through the use of activated carbon is a proven and effective method. The activated carbon absorbs organic pollutants, harmful ammonia and excess nutrients. We would like to highlight that organic pollutants such as organic acids, metabolic waste, hormones, proteins, organic compounds and antibiotic compounds cannot be removed by mechanical or biological filtration.  ADA has been known to use 100% activated carbon filtration for their Mini S & Mini M. For aquariums that do not use chemical filtration, all is not lost, just keep up with regular water changes to aid the removal of organic pollutants.

After a period of time, activated carbon would lose its absorption properties as it runs out of space to bind more pollutants to itself. Contrary to popular belief, these pollutants will not leak back into the water column when the activated carbon is spent. Most aquarium companies would recommend a changing of activated carbon on a monthly basis.

The activated carbon cartridge also performs a vital task in which the other cartridges have failed, it polishes the aquarium water, due to its compact and dense form, trapping minute dirt. On a weekly basis, we give the activated carbon cartridge a swirl in aquarium water to wash these dirt off the sponge surface, this is essential in keeping the activated carbon’s surface optimal for absorption. You will find water bypassing the activated carbon because of accumulated dirt if not for the periodic clean.

carbon cartridge | close up

For the Eheim Liberty 100/2040, one can argue that the combination of green sponge cartridge and carbon cartridge is the most effective because there are mechanical, biological and chemical filtration properties. Our preferred set up would actually be the blue sponge cartridge with a activated sponge cartridge. However, this is not possible due to the lack of space. But with the bigger Liberty models, it would be possible as their filter compartments are bigger.

Although it is rated for an aquarium up to 75 litres, we find that it is just about keeping up with our 15 litre tank. Weekly maintenance for the green sponge cartridge / activate carbon cartridge or fortnightly maintenance of the blue sponge cartridge is a must.  Another issue we faced, was a noisy impeller after some sand got sucked into the intake tube. So if you plan to use fine sand in your aquarium, we would suggest skipping this filter.

blue sponge cartridge | carbon cartridge | green sponge cartridge

If you have space of a cannister filter, we would recommend the Eheim Classic 2211 over the Liberty 100/2040. The Classic 2211 has about the same amount of flow as the Liberty 100/2040 but 4.16x the amount of filtration space. The design of a cannister filter will also make for more effective and efficient filtration. If you have to use a hang-on filter, the Liberty series is among the best. If Eheim does a rethink and redesign of their Liberty filtration media to match the effectiveness of the cannister filter media, they will secure the crown of hang-on filters comfortably.

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credit: Eheim Asia Pacific

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