First of all, thank you for this beautiful mod <3

Would it be possible to be able to turn off mob spawning?

Tank you for your answer.

There is ways to turn mob spawning off in all versions.
In newer versions it´s simply not possibly to add conigs, due to load order.

For 1.19+, you´ll need to use a resourcepack to disable them. https://github.com/TeamMetallurgy/Aquaculture/tree/master/src/main/resources/data/aquaculture/forge/biome_modifier

There are no plans for any new config options at the moment.