We are on a filter roll here, with the GEX Slim S being the third filter to be reviewed in a week. As mentioned in the GEX Roka Boy articles, we have been impressed with the build quality and design of the GEX air-powered filters. Thus, we decided to review another GEX product that is appealing to some aquarists, by being the slimmest hang on filter in the market today.
The GEX company should be credited for having the guts to redesign the hang on filter at such a fundamental level. Other aquarium companies have differentiated their hang on filters by changing the filter media options, but no company has taken the established hang on filter design and brought it back to the drawing board.
The GEX Slim S breaks the look of the traditional hang on filter by positioning the filter pump outside the filter’s body. By doing so, the filter body can now be slimmer than usual as it does not have to have a body big enough to house a pump. In the image below, the diagram shows how GEX has accomplished this.
The GEX Slim S is really a slim filter measuring 180mm in length, 152mm in height and just 50mm across.
Here, GEX waste no effort in emphasizing how slim their filter is, compared to other competing brands.
The build quality of the GEX Slim S is of the same high quality found in all their other products. The plastics used are strong, without flex, and all parts are machined nicely. We especially liked the ‘metal’ feel that GEX gave the top cover of the filter, adding a touch of class.
The GEX Slim S is slimmer in width compared to other hang on filters, but it’s longer in length. This longer length allows it to compensate for its small width and still pack enough filter media to be effective.
For the GEX Slim filters to be effective, water must be directed in a way that it passes through all the filter media along the length of the filter before returning to the aquarium. Based on the internal design of the GEX Slim S filter body, we can see that GEX has planned it to be so. However, the second cartridge that is further from the intake will not see as much flow going through it as the first cartridge. In a Slim S body with just two cartridges, this will be a minor problem and there should not be any penalty to filtration effectiveness.
In is heartening to know that in the bigger Slim bodies, GEX has appropriately position the outlet sprout closer to the filter cartridges that are furtherest from the intake. This will force water to also flow through the outlying cartridges before exiting the filter.
The filter cartridges that GEX provides with every GEX Slim filter, is enough for that filter’s operation. For the GEX Slim S, it comes with two filter cartridges.
The filter cartridges has words in Japanese and we could not guess the functions of the different cartridges as they also look exactly the same. On the packaging’s picture, they are placed in the same position.
The only difference we can spot was one had the words “2 in 1″ and the other had the words “3 in 1″. In filtration speak, these numbers can only mean the three means of filtration; mechanical, biological and chemical. The “2 in 1″ media should encompass biological and chemical filtration while the “3 in 1″ media should encompass mechanical, biological and chemical filtration.
We hope to get the Japanese words translated and will update this article accordingly if we manage to.
The motor of the GEX Slim S is positioned outside the filter body. As seen in the picture below, water is sucked into an intake that is covered by a black sponge, it then passes through the motor and flow into the filter by the intake tube. This tube is also adjustable in length.
One slight disappointment of ours was that the plastic used to make the intake tube is not of the same great material that makes the filter body. Its slightly darker and softer, and flexes a little. But there may be a use of such a softer plastic for the intake tube. Our guess is so that the ability to extend the intake tube can be housed within the tube itself, and not fixed- on extensions that other filters employ.
For aquascapers, the extra bulk of a motor in the aquascape may not be welcomed unless flora can be used to hide it.
If you have been wondering why we have not mentioned the flow rate of this filter, it is because we cannot find any mention of one. GEX’s official website is in Japanese and we tried to track down any flow rate information for the GEX Slim S but found none.
The only information we have is that the GEX Slim S is recommended for aquarium of about 25 litres. Unlike Eheim’s more optimistic view on filter to aquarium size ratio, GEX’s recommendation of pairing the Slim S to an aquarium of approximately 25 litres is pretty accurate.
Not everyone will be pleased with the dependency of the GEX Slim S on GEX filter cartridges. Using third party filter media is possible but may not be as effective as compared to using them on traditional sized hang on filters, as the slim and long body of the GEX Slim S may impede their filtration effectiveness.
For aquarists who have aquariums on their desks, the GEX Slim S is a good choice as it saves precious desk space as these aquarists can have the aquariums closer to the wall.
GEX has proven to be a company that produces aquatic products that work, with a solid build quality and attractive design. Till date, aquarists on various aquatic forums have given the GEX Slim filters good reviews, saying that it works as well as the usual hang on filters.
If you are in the market for a small hang on filter that is slim, do check out the GEX Slim S.