The Fluval FX4 and FX6 are both heavy duty canister filters that provides filtration of bigger fish tanks. With that said, the pump output for these products may cause problems if the fish, plants and other inhabitants in your aquarium can’t handle the fast water currents.
You can take a look at this guide from Aquarium Blueprints to see how you can reduce the water flow of these filters.
What is the regular flow rate of Fluval FX4 and FX6?
The Fluval FX4 Canister Filter is able to pump water at a rate of 700 gallons per hour, which converts to 2,650 liters per hour. According to internal testing from Fluval, the internal filter circulation for the FX4 is 450 gallons per hour (or 1,700 gallons per hour).
The Fluval FX6 has an even faster pump rate at 925 gallons per hour, which translates to 3,500 liters per hour. The FX6 also has an internal filter circulation rate of 563 gallons per hour (or 2,130 gallons per hour).
What will slow the flow rate of Fluval FX4 and FX6
The flow rate of your Fluval FX4 or FX6 will eventually slow down if you don’t regularly clean the filter, rinse the filter media or don’t replace mechanical filter medias that are fully exhausted.
The organic wastes will eventually clog the hosing, foam, sponges and the other filter medias inside of the FX4 and FX6.
While a clogged filter will slow water flow, it should also eventually damage the water pump due to the added stress of trying to pushing water through a dirty canister. Therefore, we don’t recommend leaving your FX4 or FX6 canister filter uncleaned in order to reduce its water flow.
How to safely reduce the FX4 and FX6 flow rate
In order to reduce the flow rate of your Fluval FX4 or Fluval FX6 without causing damage to the canister filter, we recommend that you take the following steps:
1. First off, locate the AquaStop Valves that are sticking on top of the FX4 or FX6.
2. The valve next to “IN” is for the flow rate of the tank water being sucked into the canister filter. The valve next to “OUT” is for controlling the flow rate of the tank water being pumped out of the canister filter.
3. If your FX4 or FX6 filter is currently running and pumping out rate at their normal rates, then the adjustable dials for both should be in the full vertical position.
If the dials are in the full horizontal position, then there should be no water being pumped in or out of the canister.
4. Slowly turn the “OUT” AquaStop Valve in order to reduce the flow rate of the water being pumped out from the canister and right back into your fish tank.
5. Do not adjust the “OUT” AquaStop Valve by more than the 45-degree angle or you will be going over the recommend maximum 50% reduction and risk damaging the pump of your FX4 or FX6.
6. The “IN” AquaStop Valve also needs to be completely opened, which means the dial should be in the fully vertical position.
