Hi guys,

I currently have a Fluval U4 internal filter, and tomorrow I am going to be fitting a new Fluval 305 External filter for the tank. I need to know how I can make the switch ensuring all good bacteria is saved.

What would I need to do? Do I need to keep the sponges as well as the biological media in the internal filter, or just the biological?

Please let me know, what the best way to go about this would be?

Thanks

Id keep the U4 running till the filter is seeded, 1-2 weeks max. if you cant set the canister up on another tank this is the best way to seed it, you wont risk anything if you keep the internal running during seeding of the new guy.

Im not familiar with the U4 but if it has removable media you can put that in the new filter. If your tank has been cycled for a long time there should be plenty of BB in other places, gravel etc... you shouldnt run into any issues. Like whitedevil said you can leave them both on for a bit.

no the U's are tiny. I have a U2 on my 40B turtle tank and to be honest, I wouldnt use another fluval U ever again, when my eheim gets in this U series is getting gutted and rednecked to a decent filter unit.