Most aquarium filters now use a motor to force water through some kind of filter pad which must be replaced at intervals. However, before there were reliably sealed electric motors, most home aquariums moved water using the "airlift" principle, in which a rising column of bubbles pulled water through the filtering material. This is an elegant and just about failsafe method. Debris in the tank cannot ever jam the external air pump which feeds the filter, and if electricity is interrupted, the filter cannot lose siphon, it simply starts bubbling again when power is restored to the air pump. Many fish love to play in the rising stream of bubbles.
Hydro Sponge filters, first marketed in the 1990's, are a more recent application of the airlift. Hydro Sponge I is intended for aquariums up to 10 gallons. Made of dense, strong plastic with a weighted base which holds the sponge up away from the aquarium bottom, they dismantle easily for cleaning of the sponge. The pores within the sponge provides an enormous surface area for colonization by beneficial bacteria providing very thorough biological filtration. They can be powered by an air pump with or without an airstone (using an airstone will give finer bubbles and make less noise), or with an electric powerhead for those with larger tanks or who simply feel the need for more energetic water movement in the tank.
It is difficult to imagine such a simple device working well. Surprisingly, they are excellent, and can be used as the only filter in the tank for many applications. I've used them on tanks sized from 10 gallons up to 75 gallons, always with good results. The local fish store where I shop has an expensive trickle filter for their dozens of tanks, and every single freshwater tank also has a Hyrdo Sponge or similar sponge filter as well. Apparantly the sponge is doing something which the trickle filter doesn't?
Maintainence is as simple as the filter. When you perform your periodic aquarium water change, (20% every week) save some of the old water in a bucket. Separate the top and bottom parts of the filter and remove the sponge from the tank. Squeeze it out in the bucket. See all the stuff which the sponge removed from the water? Reinstall the sponge and refill your tank. Go have dinner with the money you saved not purchasing replacement filter cartridges.
In sum, a clever and elegantly simple device which works very well.
This review is for the Hydro I specifically, but it applies to all of the Hydro Sponge Filters.
The Hydro I Sponge Filter is the best for smaller tanks (5 or 10 gallons), just as its counterparts (the Hydro II, III etc.) are great for their respective size tanks. Other types of sponge filters exist on the market, but the Hydro ones are the most efficient because you can put an airstone down the shaft of the filter to get the water going through the majority of the sponge's surface. In addition, the sponge sucks up a surprising amount of debris and waste so it is good for a certain amount of mechanical filtration as well. As other reviewers explained, about once a month you simply squeeze the sponge "clean" in the tank water sitting in your bucket during the water change in order to ensure that you don't kill the bacteria by using chlorinated tap water. The water generally becomes dark brown or black, and you get a sense that you have really cleaned the tank well. (For the more squeamish types, the sponge smells like healthy earth so it is completely inoffensive. You can then use this water to feed house plants some nutrients, if you want!)
Pros: I am a great proponent of the use of sponges because I have never had problems with water readings as a result of using biological filtration. Sponge filtration is much, much more than a backup for canister or hang on power filters that clean a large number of gallons per hour. Biological filtration keeps the tank clean using beneficial bacteria and aerates the tank at the same time. Using a gang valve, you can aerate a little or a lot, depending upon whether the type of specimen you are keeping likes currents or calmer water. The biological force of a sponge filter is such that you can start a new tank by lifting a cycled and seasoned sponge filter from one tank and putting it into another. If you take some seasoned gravel too, you can immediately add a tankful of fish without worrying about ammonia spikes etc. Most importantly, I love sponge filters because when you are medicating your tank and have to remove the carbon from your filters for the antibiotics or drugs to be effective the biological filters continue to keep the denizens of your tank alive during this potentially disastrous time in your tank's life (eliminating parasites or diseases can last for up to two weeks). These Hydro sponges are soft, so amphibians or sensitive fish do not get roughed up when they brush against the sponge. If you clean your sponges regularly (once a month minimum), you will only need to replace the sponge if it loses its shape and no longer fits around the plastic rod. If you neglect cleaning, I would imagine that the sponge might get so gummed up with debris that it would no longer be absorbent and you would need to replace the sponge at that point.
Cons: The only disadvantage is the way they look--sort of like tiny little nuclear power plants in your tank--so you strive to find ways to hide them behind rocks, decorations, or large aquatic plants (or be creative and incorporate them into the decor by, say, having a theme like "post apocalypse" or "industrial age"!) Granted, I have tended to use a larger sized sponge than is recommended by the manufacturer, as I do not think it is possible to overuse sponges since the beneficial bacteria reproduce according to the amount they are fed. However, even if you get the proper sized sponge for the tank, they are difficult to conceal.
Overall, given the pros and cons, I love my amphibians and fish more than the look of their tank, so I avidly use sponge filters to keep them alive and happy. I like Hydro the best because of the possibility of using an air stone and because I like the softness of the sponge.
Buy Hydro-Sponge Filter I--HS910 - Aquarium Technology, Inc. Now
I bought this sponge filter for my angelfish, who were suddenly spawning every week. The babies were not able to survive if I left the regular filter on. I ended up having to move them to a ten gallon tank, and thus the need for this filter.
I have to say, I've never had a better filter. You attach an aerator line to the inside, and that's the only thing you need. The air bubbles oxygenate the water while they also work to draw water through the sponge. All the muck that usually accumulates pretty quickly in my tank was drawn in, and the sponge works to break it all down naturally, which is actually healthier for my fish and plants. And no babies were harmed by this little device. it's gentle, but effective.
And the best part is that you do not have to buy filters! Just rinse and squeeze the sponge under room-temp water for a moment and you're done. I'm definitely going to replace my old money-devouring filters in my 55 gallon tank with some like this. These are well worth buying, and actually pretty cheep considering it all. I advise anyone thinking of getting one of these to make the leap. You won't be sorry.
Read Best Reviews of Hydro-Sponge Filter I--HS910 - Aquarium Technology, Inc. Here
I bought this for my Axolotl tank as I needed a sponge filter so they couldn't get their little fingers or gills stuck in the filter uptake. I was very happy to find one at such a great price and with such great reviews so ordered it immediately. Upon arrival I discovered just how huge this monster is! I should have read the dimensions listed (though would have gotten it anyway) so I would not have been shocked by the size. A 4 1/2 in diameter takes up a huge amount of space in a 10 gallon tank (they are like what, 18 by 12?). Just a heads up for people looking at this product. Even with the huge size, this product seems to be working good and I have no complaints with it. I actually find the bubbling sound of the top quite soothing. :)
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what can i say? a simple sponge filter perfect for a 10 gallon tank that houses anything small that a power filter might suck in. baby shrimp, fish fry, etc. low maintenance, low cost, low electricity use. great filter.
This is a nice kit, I really like the case. It does have every test you would need for a planted freshwater and a saltwater tank.
