Perlite as a filter media?

[Hooked]

Hi,
I was chatting the other day to an engineer that had a hand in setting up a bunch of tanks involved in experiments doing gene studies on fish. I was interested in the canister filter systems, specifically what media they used. They used Expanded Perlite as a filter media due to its large surface area over other medias.
Perlite is used widely in heavy industry to remove heavy metals out of solution. Its also a popular media in hydroponics. From memory its very cheap.

A bit of copied info:

Perlite is a naturally occurring dense, glassy volcanic rhyolitic rock and can be expanded up to 20 times its original volume when heated rapidly at 800-1200°C. Expanded perlite (EP) acts as an excellent insulator, both thermal and acoustical, resists fire and is classified as an ultralight weight material. The expanded perlite is white in color, and has a density of about 32 g/L. Perlite is generally chemically inert and has a pH of approximately 7. The specific surface area of expanded perlite is 1.89m2/g.

I'm just interested if anyone has any experience with Perlite as a filter media and if there are any draw backs? Also I'm interested in the specific surface area of the other common media's we use if anyone has the stats?


Cheers

[ILLUSN]

works great in a filter bag.

pros:
Cheap
Chemically inert (wont effect water chemistry)
Excellent surface area

cons:
Small particle size needs to be in a fine mesh bag
fine mesh bag can clog reducing filter capacity hence need to clean filter often at least once a fortnight

Lots of Dust needs to be thoroughly washed.

Soft can grind down into a powder quite easily so will need to be changed often (every 6 months).

[Hooked]

Hi Illusn,

Thanks for the info. I just saw a post where you recommend Hydroton, expanded clay balls, as a filter media. I'll have to look into that,

Cheers