Here's a pretty standard question I'd like you all's opinion on:  For my 10g I have a standard HOB filter (Tetra Whisper) with what they call a 3-way filtration system.  The bio-foam stays in but the filter pad with carbon I'm supposed to change.  I'm sure you know the drill.  How often should I be changing the pad providing mechanical and chemical filtration?  I have a moderate fish load (5 - 1.5" fish + 1 ghost shrimp).  My water changes/gravel vac is about 20% once a week.

Change it when it looks dirty.  I usually change mine every week to ten days.  I go around the tanks and check them, and if they don't look dirty, I leave them in until they do.  In tanks with a light fish load, they may not need changed for a couple weeks or more. 

coming from someone that's had 15 of the lil HOB sobs running at one time they get costly to change pads weekly. it's perfectly fine to wash the filters and reuse. the carbon in general is good for about a month after that is useless. but on the other hand i've been running my tanks with no carbon for about a year and a half with no adverse side effects. so i'd defintely recommend washing and reusing at least a few times and take the saved money and invest in something else for the tank

 I agree with BuK- just wash them out.

If you have a problem that requires constant carbon filtration, you should fix that at the source, not bandaid it with a filter cartridge.

It's mostly marketing, I think.

If you aren't using carbon, (and I usually don't) get some bulk filter material and cut your own pads.  It will save you a lot of money!

As mentioned above, you can just buy some aquarium cotton (Keep the plastic frame of the cartridge in). You also have to buy a carbon back though (no biggie, like a $1 or $2).

The only problem with loose carbon is if it gets in your propeller, its near impossible to get all the little strong off, new propellers aren't typically expensive, not that you want to go around swapping them all the time

I know PetSmart sells the aquarium cotton, I don't know which other stores carry it

hc8719 said :

As mentioned above, you can just buy some aquarium cotton (Keep the plastic frame of the cartridge in). You also have to buy a carbon back though (no biggie, like a $1 or $2).

you won't need the carbon unless your trying to remove medications or if your water is unclear (if unclear i recommend fixing the cause not covering it up). also if your interested in making your own pads i use an e-bay shop for my replacement w/d pads. they're the pink type that actually filter finer particles than the blue and i got 20 12"x12" pads for about 21 buks shipped

I don't use the loose floss, I get a bonded pad like this:

www.drsfostersmith.com/product/prod_display.cfm

You can buy this in stores, too.  Ocean Treasures has a plain bonded pad that works well in the HOB filters that's even cheaper.

The Ginger company is based in Toledo. And they make filter cartridges that work well and can stand up to a lot of washings.

www.gingerinc.com/