Good advice above! The water changes to get the water as similar as possible is a good option. When you can, anything you can do to get it as close as possible in all ways of course is best.
Really the issues might be about the new substrate not matured. What substrate is this? Is there a chance of leaching ammonia?
I would take the old filter before cleaning rinse gently into the new tank. Add info edit: Because it helps seed a little BB into the substrate.
Otherwise since the Planaria treatment, I would normally recommend adding the old substrate to a filter bag and let it sit into the new tank for a month or 2.
Since the Planaria issue you could do another treatment with the substrate in the old tank, and then gently soak it / rinse it out with treated water extra Prime. Use in the new tank.
BB would assist in the transition.
You said you would be adding over to the new tank A couple of the primary plant structures. Spiderwood and Cholla which would be really helpful and likely enough. Still maturity in a tank improves success. Especially with shrimplets if you have them on the way.
Food for thought.
Mostly you do not have a biofilm rich environment for the shrimp. Since there was a Planaria treatment which can kill snails, I would wonder that the treatment might kill aufwuchs and make biofilm dead or not nutritious any more. Since I am not learned in the deep scientific aspects of this it is a thought/guess.
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