How often do you replace filter cartridges?

[SalviniCichlidFan]

I have an aqueon quiet flow 75 hang-on filter that has 2 filter cartridges in it. How often should I replace the filter cartridges with a new one?

On one hand, I don't want to disrupt the established bacterial colony in the old cartridge, but on the other hand, I don't want the cartidridge to be too dirty.

 

[Deadeye]

Usually I will do it every month - but this depends on how dirty they are getting. If mine aren’t visibly caked up in grime to keep from doing their job, I don’t change them out.

 

[FJB]

I never discard them.
After first setup (years ago), I modified mines in a couple Penguin filters to be non-disposable, washable, and long lasting.
Money savings, permanent bacteria colonies, not supporting exploitative commercial enterprises from the pet care industries, nor the 'disposable culture', are among the benefits I perceive (just for myself, but I don't mind sharing my views).

 

[Fallen_Leaves16]

The reason filter cartridges need to be replaced is because the activated carbon in them stops working once it's absorbed as much "stuff" from the water; it's honestly not really worth using carbon in my opinion as not only does it stop working after a relatively short amount of time, but it renders nearly all medications useless when it is "active". If not replaced frequently, they serve only as a flimsy and somewhat inefficient means of removing large waste items from the water and a place for a bacterial growth to occur; there are vastly superior products (namely sponges) that do the same. Like F FJB , I just use other non-carbon media (sponges, lava rock, and the like), though his idea of incorporating it into a cartridge of sorts is quite clever (might have to try it sometime, if you don't mind me stealing your idea )

 

[fishguy1978]

I throw them away when the box gets opened to setup a new filter. Purchase either the appropriate sized Aquaclear sponge insert or purchase some poret foam and cut to size. Now you have a cost effective and significantly better filter.
I don’t use carbon. It works great but once saturated it will begin leaching back into the water column. Regular water changes are better.

 

[SalviniCichlidFan]

The reason filter cartridges need to be replaced is because the activated carbon in them stops working once it's absorbed as much "stuff" from the water; it's honestly not really worth using carbon in my opinion as not only does it stop working after a relatively short amount of time, but it renders nearly all medications useless when it is "active". If not replaced frequently, they serve only as a flimsy and somewhat inefficient means of removing large waste items from the water and a place for a bacterial growth to occur; there are vastly superior products (namely sponges) that do the same. Like F FJB , I just use other non-carbon media (sponges, lava rock, and the like), though his idea of incorporating it into a cartridge of sorts is quite clever (might have to try it sometime, if you don't mind me stealing your idea )

How does lava rock filter water? I have one in my aquarium as well, but I never understood the concept. Also, I have this piece of coral rock with lots of powers on it. Does that also have the same filtering effect?

 

[neutrino]

Lava rock is meant to be a bio-media, in that it provides a surface for beneficial bacteria rather than "filtering" in the sense of clarifying water by capturing particles. Lava rock is highly variable and often not the most efficient in terms of surface area per volume.

I have this piece of coral rock with lots of powers on it.

Did you mean pores?

3 main types/functions of filter media:
Mechanical media-- Acts as a strainer to physically remove particles and debris, sponges, foam pads, and filter floss do this, some canisters use a type of ceramic rings to theoretically improve flow through the filter and trap some heavy debris.

Bio media-- Provides the surface area where beneficial bacteria can live. All manner of materials can be used, specialized ceramic, sintered glass, etc., various aqaurium sponge and foam products, other (non toxic) foam, sponge, etc., including pot scrubbers, to mention a few. So sponge and foam does both (technically, so does poly fiber if you leave it in long enough). The point of being porous is to provide a lot of surface area per volume of media, which is where a lot of debates start and where some materials are better than others. Fiber/carbon cartridges tend to be minimally efficient (and less cost effective) vs most other options.

Chemical media, like carbon-- Removes medications and some chemicals and organic substances (not ammonia or its derivatives). As mentioned, carbon has a limited useful life that varies according to how much you use, which type, what you're trying to remove, etc. Chemical media is optional in most cases.

 

[Iwhoopedbatman]

I'd recommend replacing it with a sponge to save money, but if you want to keep it simple, just wait until it's causing water to back up and exit via the overflow of the filter and then switch them out. If you do switch to sponges, that's also when you rinse them out.
In defense of carbon, if you don't fully trust your local water source, it has it's value. I also think it provides a little stability that can be invaluable to new fishkeepers. I usually recommend people just starting out to use it until they feel like they have a good feel on how their tank functions. Personally, I don't trust my local city water at all, so I use it in most of my tanks. I add some food grade resin and GFO to make a homemade chemipure.