Old/new filter overlap period

[SwissTrees]

Hey guys and gals

So I have an Aquatop CF300 that's been running on my established 40 gallon tank. I recently got a fluval 306 to replace it with and have had it running along side the Cf300 since November 2nd (14 days as of this post) I eventually want to remove the CF300 but want to make sure the fluval has grown enough BB to not throw the tank into a mini cycle.

Any thoughts on how long I should wait before removing the 300? Its not like I can test the water as if it was a totally new tank cycle to see when it's ready.

How have you guys gone about a swap like this?

Thanks!

 

[deeda]

I prefer to leave both filters running together for a couple weeks or transfer most of the mature media to the new filter if possible.

 

[convict360]

2 weeks is safe imo

 

[thacarter546]

If the cf300 is running functioning and both filters are not too much current why remove it?

 

[Drstrangelove]

If you can remove the old media (from the old filter) and place some of it (e.g., half) in the new filter, I agree that you should be fine now after making that swap.

You *might* be fine taking down the old filter at this point. The point is that while BB are everywhere in a tank, the old filter is likely where most of them still are to be found. The new filter would have some but far less BB at this point.

I would give the process 2-3 more weeks. In this case, there's really no upside for doing things early (maybe one saves a dollar or two of electricity.) OTOH, the possible downside dwarfs that by miles and you might find yourself regretting doing something you had no reason to rush doing.