I have set up my entities to spawn using json files in data/modid/forge/biome_modifier directory like so.

{
  "type": "forge:add_spawns",
  "biomes": [
    "minecraft:swamp",
    "minecraft:beach",
    "minecraft:mangrove_swamp",
    "minecraft:ocean",
    "minecraft:river"
  ],
  "spawners": {
    "type": "modid:mob_name",
    "weight": 899999,
    "minCount": 1,
    "maxCount": 1
  }
}

However, when I am not in one of the spawn biomes, there is an acceptable number of spawned entities 7-8 and only 357 entities in total. However, as soon as I go to one of the spawn biomes, hundreds of my mobs immediately spawn and the entity count jumps to 3500+. Now after just sitting in the biome for a while, thousands of each entity type have spawned and the total entity count is crazy at 15,833! How do I limit mob spawning, since the weighting doesn't seem to work?

I looked up how Forge does it for the forge entity list but the level.getEntities().getAll() command is protected in the Level Class and not available within the checkSpawnRules function.

Spawning works if you set all the weights to 1.