The dutch translation of this page still needs to be reviewed, it is highly inaccurate, incomplete and probably full of errors! It is only a rough translating by Google Translate!

7.2.1. Polyester Floss

Polyester Floss is usually only used for mechanical filtration. It is rarely used for biofiltration. This article goes into why polyester floss has to be used this way.

Our Data

The very rough approximation for the biofiltration capabilities of polyester floss fibers is as follows:

Polyester fibers are used in three distinct types of filtration:

  • Mechanical filtration (very common)
  • Polishing filtration (often tried but rarely succeeding)
  • Biofiltration (rare)

Poly-fil (polyester filter floss) is made from fine polyester fibers. This is just good old cheap pillow filling from the craft shop. Some hobbyists use packed Poly-fil as a polishing filter. The tortuous paths created by the fine fibers can even filter out bacteria. This can give very crystal-clear water.

But one needs to be cautious here. The automatic temptation is to just stuff a canister or a hang-on-back filter with tightly packed Poly-fil and go away. But aquarium water is dirty water. It will have a lot of particulate in it. So a tightly packed Poly-fil polishing filter in an aquarium can clog very rapidly, requiring frequent cleaning.

Amatitlania myrnae
Amatitlania myrnae

Also virtually all aquarium pumps are low pressure pumps. Packed Poly-fil resists the flow of the water and creates a back pressure which can severely impact the flow of water through a filtration system. It can reduce the flow to a trickle.

So, a packed Poly-fil filter becomes impractical. It requires a high-pressure external pump (typically a pool pump) be added to the system and it requires frequent cleaning (like once a day in extreme cases). Not something for the average hobbyist.

If a large amount of Poly-fil is very loosely packed in a very large low flow (MUST BE LOW FLOW AND VERY LARGE!) rate filter (think a 55-gallon drum or a trash can filter) it is a great media both mechanical and biofiltration and will last for months.  Polyester fiber in a filter can also turn into a good biomedia if it meets some conditions:

  • The fiber is not packed in tightly
  • The aquarium is lightly stocked
  • Feeding is light
  • Food has a high protein content (>45%)
Panda Goldfish
Panda Goldfish

Other Forms of Polyester Fibers

Bonded polyester fiber pads (“pinkie” pads are one type of bonded polyester pad) are a common mechanical filtration media. These pads are typically replaced or cleaned once a week and don’t really have time to build up any level of biofiltration capacity. So, we don’t consider them biofiltration media. But the pads can function as biomedia if the four conditions above are met.

These pads work well in sumps where the pads are easily replaced in minutes. Using them in a canister will require about half an hour of maintenance time per week.

Aquarium Pinkie Pads
Aquarium Pinkie Pads

Many hang-on-back filters utilize fuzzy polyester bags to hold a filtration media such as activated carbon. The bags are good mechanical filters but are far too small to be effective biofiltration devices.

The polyester fabric in biowheels is an ineffective biomedia as it has very little surface area, on the order of one to two square feet.


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