After researching a number of different filters for my 20-gallon gourami tank, I decided to give this one a try. It is designed with function in mind, including an adequate system of bio-filtration and flow control. Flow control, though simple in design, is a nice feature to have that is sadly lacking on many HOB filters. This feature was important to me as gouramis are labyrinth fish who prefer slow-moving water, and I wanted the ability to adjust the flow, if necessary.
One reason I hesitated to invest in this filter is that, although the filter itself is very reasonably priced, the replacement filter cartridges are somewhat expensive. Fortunately, the size of the intake tube is just right to use one of these pre-filters: Pre-Filter Sponge 3 Pack for Fluval Edge Aquarium This increases the biological filtration even more while filtering small particles before they ever enter the filter itself. I simply rinse the pre-filter in aquarium water ever two weeks or so and replace the filter cartridge once a month, since activated carbon expires monthly. Rinsing the pre-filter is an easy step, since this has an extendable intake tube, making it easy to detach the endpiece from the filter itself without having to actually pull the sponge off the intake every time. The filter even continues to run while I do this, as long as the end of the intake is submersed. As an added bonus, my flower shrimp loves to eat the particles of food that collect on the sponge, and as a filter feeder, she enjoys the luxury of hanging on the intake to make use of the flow without the danger of being harmed by the filter intake. Meanwhile, between some tinkering with the flow control and the addition of the sponge, the flow itself is weak enough to not upset my male/female pair of gouramis, who are able to blow bubble nests and engage in spawning behavior. Even though this is only a 20-gallon tank, the flower shrimp, clown pleco and mystery snails have their own space, and the gouramis have theirs. Having a sponge pre-filter and flow control also benefits the live plants in my tank, especially the java fern, which proliferates easily and abundantly, but often can be damaged by filter intakes when the young ferns float about the tank before finding a piece of driftwood or other material where they can grow.
In terms of reliability, I have run this filter steadily for four months as of the writing of this review, and, used in conjunction with some additional sponge filters, this has proven itself to be reliable. It is self-priming and consistently restarts automatically following a power outage. It even runs steadily during a partial water change, and the 'Bio-Falls' system seems to provide additional aeration for the water, which is important not only for providing oxygen for my water-breathing creatures, but helps remove toxic substances, which benefits all of the creatures in my tank, including the air-breathing gouramis.
To conclude, I will provide a brief list of pros and cons:
PROS: 1. It is inexpensive 2. It is effective in terms of mechanical, chemical, and biological filtration 3. It is reliable and self-priming 4. It fits the inexpensive Fluval sponge pre-filters 5. It has flow control
CONS: 1. Replacement cartridges are not easily found in stores 2. Replacement cartridges are expensive (but this can be easily addressed by using an inexpensive sponge pre-filter, extending the cartridge life to at least a full month)