Net files

Any item can be a net. Each file in data/<namespace>/net/ defines one:

{
  "item": "minecraft:cobweb",
  "style": "iron",
  "catchTimeMultiplier": 0.85,
  "luck": 1.5,
  "bonusCatchChance": 0.05
}

Field	Type	Meaning
item	item id	The item that goes in the net slot
style	plastic, copper, iron, gold, diamond or netherite	Which funnel look the trap shows
catchTimeMultiplier	number from 0.05 to 10, optional (default 1)	Multiplies the bait's wait. 0.5 catches twice as often.
luck	number, optional (default 0)	Added to the bait's luck for the catch roll
bonusCatchChance	number from 0 to 1, optional (default 0)	Chance of a second catch roll in the same cycle, without using extra bait

style only chooses one of the built-in looks. New looks need a resource pack that replaces fishtrap:block/fish_trap_funnel_<style>.

Changing built-in nets

Overwrite a file at the same path, for example data/fishtrap/net/gold_net.json. If two files use the same item, the one whose file id sorts last wins, and the server log notes it.

Catches that need a net

The trap passes its net to the catch roll as the loot tool (or a fishing rod when no net is fitted). A catch table entry can require a net with vanilla's minecraft:match_tool condition:

{
  "type": "minecraft:item",
  "name": "fishtrap:rainbow_fish",
  "weight": 1,
  "quality": 1,
  "conditions": [
    {
      "condition": "minecraft:match_tool",
      "predicate": { "items": "fishtrap:netherite_net" }
    }
  ]
}

JEI and this wiki show that requirement, as long as items lists item ids rather than a tag.

Current values

Net	Catch time	Luck	Bonus catch
No net	Normal	0	—
Copper Net	10% faster (×0.9)	+0.5	—
Iron Net	20% faster (×0.8)	+1	10%
Gold Net	20% faster (×0.8)	+2	15%
Diamond Net	35% faster (×0.65)	+2	25%
Netherite Net	50% faster (×0.5)	+3	40%