Prepare an 8 x 8 baking dish by lining it with parchment paper and spraying the parchment paper with cooking spray. Set aside.
Open your Swedish fish.
Melt Swedish fish and 400 grams water on low - medium heat in a medium sized pot.
While the Swedish fish are melting, bloom your gelatin.
Bloom gelatin by whisking together 200 grams of cold water with 40 grams of unflavored gelatin in the mixing bowl of a 5 quart planetary mixer. Let it sit, undisturbed, until Swedish fish are melted.
Once Swedish fish are melted, pour the syrup over the gelatin.
Turn the mixer on low for 30 seconds to combine the syrup and gelatin.
Increase the speed to high and let it mix for 10 minutes.
Turn off mixer. Pour Swedish fish marshmallows into prepared pan.
Place another piece of oiled parchment paper on top of the marshmallow, creating a seal.
Let Swedish fish marshmallows sit for 12 hours undisturbed before cutting.
After 12 hours, oil a sharp knife and cut marshmallows into desired size. 2" x 2" is recommended.
Toss marshmallows in powdered sugar.
Store in an airtight container.