I have a Fluval 305 and over the years have done different things with the carbon sections.

At first I would just buy a big jug of carbon and pour enough into each section to almost fill it. One problem with this is whenever I reconnect the filter there's always a cloud of carbon shot into the tank no matter how many times I'd rinsed the carbon off in the sink before putting it into the filter. Another problem is little bits of carbon that get up into the bio media, the pump, and everywhere else.

The obvious solution at first seems to be to put the carbon into bags and place those into the sections, but this solution has problems too. The biggest is that the bags - no matter how I try - won't completely fill the sections and leaves too much bypass space. A lot of water would pass around the carbon without ever being treated. A much smaller issue is the extra time and trouble it takes to fill the bags, tie them off, clean the spilled carbon, etc.

Neither option seems to be a good way to put carbon into the filter and I'm hoping somebody has come up with something else.

Any suggestions?

Carbon is only marginally needed in an existing stabilized aquarium. It removes odor-causing particulates that can give a tank the "pond smell" as I like to call it. It also helps clarify the water, but only minimally so. The main reason I would have carbon is after a medication bout the only way to filter out the meds is through carbon. So I would say go with the bags, since you don't need 100% exposure, or another option would be to layer the carbon in the chamber between two layers of filter floss. That should help keep the chunks where they need to be.

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Officially fishless until after the move....tune in later for details!

That's interesting. For the past 10 years or so of keeping the aquarium I've had the bottom two sections filled with carbon and the top one with ceramic rings for bacteria growth.

If what you're saying is true, I should just have the bottom section contain carbon and the top two sections have the ceramic rings.

Yes, or do the middle chamber as floss/foam to keep the carbon bits from getting through. Sorta like a strainer.

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Officially fishless until after the move....tune in later for details!

Fluval has water polishing pads that you can use in your top section, this will all so help keep water clear..