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Tank upgrade advice (Betta fish)


26 Oct 2020
Aberdeen, UK
I'm upgrading my Betta from a 20l with external oase filtosmart 60 to a 57l flex which arrives today.

I want to use the biological media out of the oase to seed the flex but obviously need it to run for a couple weeks more while the flex establishes for him.

What do you think is the best course of action?

1) use half the media from the oase and leave it running only half full (top up flex with new)

2) use all the media and top the oase back up with new on the premise that the filter body, sponges and tank contents will contain enough bacteria to continue for a couple weeks.

The 20l is planted to about 60%(although some will be moved so about 40%) and the bioload is none existent (single Betta and some RCS).


15 Nov 2015
Either plan seems sensible. Bacteria will multiply exponentially with the correct food source and conditions so it's not massively important. You could just chuck half the media from your own filter into the new and you'd be fine. The one good thing about a slower swap over is it gives your shrimp a more stable environment and shrimp don't tend to like new tanks so they would be what I was more worried about than the betta.

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