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Fluval Canister Filter: 306 vs. G3

If you are looking for a canister filter that can handle a fish tank of up to 70 or 80 gallons, then Fluval has a pair of products that you might want to check out with the 306 and G3. So which of these is better? You can find out in this comparison guide.

Quick Summary

When it comes to performance, we found that the Fluval 306 Canister Filter is the better of the two since the bigger size gives it more room for filter media. Not to mention that it also has better filter circulation in addition to using slightly less energy.

With that said, the Fluval G3 Advanced Filtration System does have some notable advantages. The biggest of which is the HydroTech Performance Monitor, which will help you check the status of your filter media, total dissolved solids, temperature and flow rate. The G3 can also pump water faster when compared to the 306.

If you want the best filtration, we recommend picking up the 306. If you want an easy way to monitor your filter media, TDS, temperature and/or flow rate, then you might want to get the G3 instead.

You can purchase either product on Amazon with the following links:

Fluval 306 vs. G3 Comparison Chart

 Fluval 306 Canister FilterFluval G3 Advanced Filtration System
Dimensions10" x 7" x 18" 9.8" x 9.8" x 9.72"
Aquarium TypeFreshwater


Brackish Water


Brackish Water
Aquarium CapacityUp to 70 gallons Up to 80 gallons
Pump Performance 365 gallons per hour at 120V/60Hz

340 gallons per hour at 240V/50Hz
303 gallons per hour
Filter Circulation206 gallons per hour185 gallons per hour
Wattage16 W at 120V/60Hz

15 W at 230-240V/50Hz
18 W at 120V/60Hz

17 W at 230-240V/50Hz
Filter MediaBio-Foam+ Sponge

Bio-Foam Filter Block

BioMax Ceramic Rings


Fine Filter Water Polishing Pads
Biological G-Nodes

Chemical Cartridge

Pre-Filter Cartridge
Autostop Valve?YesYes
Media StorageBasketBasket

HydroTech Performance Monitor?NoneMaintenance Scheduler



Water Flow
PricingCheck price on Amazon.Check price on Amazon.


The Fluval 306 is quite a bit bigger compared to the G3. The 306 is a little bit longer while the G3 is wider. The main difference is the height as the 306 is nearly twice as tall as its competition.

The bigger size means that there are more room for biological, mechanical and/or chemical filtration. So the 306 has the advantage when it comes to keeping your water clean. You can find the exact measurements for both products below:

  • Fluval 306: 10″ x 7″ x 18″
  • Fluval G3: 9.8″ x 9.8″ x 9.72″

Aquarium Type

Both filters can be used on freshwater, saltwater and brackish water fish tanks.

Aquarium Capacity

The Fluval 306 Canister Filter has been rated for aquariums of up to 70 gallons while the Fluval G3 Advanced Filtration System has been rated for aquariums of up to 80 gallons.

Pump Performance

The pump performance for the Fluval G3 is different depending on the wattage being used. At 120V/60Hz, the pump can move 365 gallons per hour. At 240V/50Hz, the same pump can move 340 gallons per hour.

In either case, the G3 is still faster than the 306, which can still move a respectable 303 gallons per hour.

The Fluval G3 Advanced Filtration System on Amazon.

Filter Circulation

The Fluval 306 does have better filter circulation at 206 gallons per hour. That is more than what the Fluval G3 can produce, which is 185 gallons per hour.


The 306 filter also consume slightly less energy. It requires 16 W at 120V/60Hz  or 15 W at 230-240V/50Hz. In comparison, the G3 filter requires 18 W at 120V/60Hz or 17 W at 230-240V/50Hz.

Filter Media

Both the 306 and G3 come with all you need to get started.

The Fluval 306 offers biological filtration (via the Bio-Foam+ Sponge and BioMax Ceramic Rings), mechanical filtration (via the Bio-Foam Filter Block and Fine filter Water Polishing Pads) and chemical filtration (via Carbon).

The Fluval G3 provides biological filtration (through the Biological G-Nodes), mechanical filtration (through the Pre-Filter Cartridge) and chemical filtration (through the Chemical Cartridge).

As we stated above, the bigger size of the 306 means that you can fit more media into the canister when you compare it to the G3.

The Fluval 306 Canister Filter on Amazon.

Autostop Valve

Both products come with an autostop valve. The accessory is designed so that you can easily stop the water flow through the tubing if you want to remove the top of the canisters.


For the uninformed, you need to add water to your Fluval canister filter before powering it on. To do so with the Fluval 306, you have to continuously use a less-than-ideal handle to pump water from your fish tank into the canister. The resistance will become progressively stronger as you pump. You will know that the canister is filled once you see water coming out of the filters output nozzle and into your tank.

With the Fluval G3, you only need to press on the primer button several times to fill up the canister for use. This method is a lot faster in addition to being easier on your hand and wrist.

Media Storage

The Fluval 306 Canister uses baskets to hold filter media while the Fluval G3 Canister uses a combination of baskets and cups to hold media.

HydroTech Performance Monitor

The Fluval G3 Advanced Filtration System comes with the HydroTech Performance Monitor, which provides a few nifty features.

The first of which is a maintenance scheduler, which monitors the cleaning intervals between the biological, chemical and mechanical filtrations. This is especially helpful if you are using chemical filtration, as you need to regularly replace carbon and other similar types.

The other feature of the HydroTech Performance Monitor its is ability to measure Electrical Conductivity. The sensor will measure the total dissolve solids (or TDS) in your fish tank.

If you are keeping common fish in the aquarium hobby, then you most likely don’t have to worry about the TDS metric. If you are keeping sensitive and/or uncommon fish, then the TDS metric can be helpful in keeping your pets healthy.

The monitor can also keep track of the temperature in your fish tank. While an aquarium thermometer is not that expensive to purchase, having one built right into your filter is rather convenient.

Last but not least, the monitor can also measure the flow rate. This could be somewhat helpful knowing how much your water is filtered in your fish tank. Ideally, you want your canister to filter the entire volume of your fish tank several times over the course of an hour.


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