+1 to the Prime comment. Regardless of what's happening, be it rock die off, animal die off, bacterial bed disturbance, etc. etc. etc., the first and major outcome of all of them will be ammonia production. If you catch it early, you should be able to ride out the cycle using prime and prevent anything you paid for from dying. There's not much else you need to worry about during a transfer IMO.
If you start to detect ammonia using a salycilate ammonia test like the API kit, add prime until your test for ammonia comes back negative. Prime will make the ammonia invisible to a salycilate test kit (unless you let the test tube sit for too long). Remember that if you do detect ammonia, you're likely going to go through at least a week or longer cycle, and prime starts to break down after 48 hours, so you'll need to stay on top of testing and dosing.
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