Minecraft 1.20.5 has changed syntax on many commands, so most commands will no longer work without an update.
An update is in progress, you can check compatibility progress here.
Loading
Page
Try the Commands Troubleshooting and Help page if you get stuff with server errors.
Minecraft Cod Fish NBT Data Tags
Using the summon command to spawn in a minecraft cod fish is simple, take the command and enter into chat and presto you have a cod fish.
Summon cod that will not despawn
Fish placed with buckets do not despawn naturally, the {FromBucket:1} tag can be set to make them perminant as if they were from a bucket.
/summon minecraft:cod ~ ~ ~ {FromBucket:1}Suggestions or found a bug
Leave me a comment/like on:Minecraft Versions Permalinks
If you're looking for a particular summon mob generator you can link to these specific versions of the command generator.