There are many types of filters that use a box hanging off the back of the aquarium to mechanically filter the waste. These are called hang-on-back, HOB, or cartridge filters.
Author: David Bogert
The author, David Bogert, is a certified chemist, something that is only useful in the sections on chemicals such as conditioners and fertilizers. He has about 43 patents, mostly in the medical device field, which only helps with some DIY designs. But he also spent much of his life as a scientific researcher working on literature research, data analysis, statistics, and a little-understood field called "experimental design." This experience is very applicable to ALL fishkeeping science. The author has been keeping all kinds of aquariums and all kinds of fish for over 54 years. He currently has ten large and many small aquariums. But note that he is not an "expert" in all aspects of aquarium keeping. The ecology of an aquarium is far too complex for anyone to be a true "expert" in all the different aspects. One can only search the journals and books for relevant research in each individual subject.
8.1.1. Aquarium Filter Test
Aquarium Filter Test: how “good is a filter?” Most focus on ammonia and nitrite oxidation but forget Crystal-clear water!
8. Review of Aquarium Filters
Any discussion of ANY filter requires a disclaimer. ALL commercial filters almost without exception tell the owner to replace the filter media! Replacing the Filter Media is a Big SCAM!!!
7.4.8. Chemi-pure Filter Media for the Aquarium
There are several varieties of a “Proprietary Product” called Chemi-pure. These are simply mixtures of the products below with very high price tags.
7.4.7. Poly-Filter in the Aquarium
Poly-Filter is an extremely expensive ($45 for a one square foot piece!) fibrous pad material that is commonly used in filters. This material is basically disposable baby diapers per the chemistry in the patent.
7.4.6. Purigen in the Aquarium
Seachem Purigen is an interesting well hyped extremely expensive ($45-$60 for one liter) product that is supposedly unlike any other filtration product.
7.4.5. Phosphate Removing Granules for the Aquarium
Phosphate removing granules work! So if a 95% water change doesn’t remove the phosphate, phosphate-removing granules are a very good option.
7.4.4. Zeolite Ammonia Removing Granules in the Aquarium
Zeolite Ammonia Removing Granules in the Aquarium in the aquarium is to expensive and it removes just too little compared to a normal functioning filter!
7.4.3. Ion-Exchange Resins in the Aquarium
There are two distinct uses for deionizing resins. One is to treat water for a water change and one is to directly treat the aquarium water to remove nitrates or ammonia. Neither use is a very good use of monetary resources, to put it mildly.
7.4.2. Activated Carbon in an Aquarium Filter
Activated Carbon in an Aquarium Filter has very limited use. The way manufacturers advertise is a scam!
