Besides your losses ... glad to hear it's going well
Sounds like you have a good plan and you should do just fine
Don't forget that you can use things like Ammo Lock or AmGuard if you have a serious issue
Then you can do a WC without freaking out
Don't fret the nitrites you are seeing. Just keep more than one foam in the filter and only rinse them ( one per session ) in old tank water ... unless they become so plugged you have to toss them
What I do in my 20g QT ( Aquaclear 50 ) is rinse the bottom foam and exchange it with the top one
You can do either/or and keep rotating them without losing beneficial bacteria
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