I implemented a custom fluid like this:

The registering of the Fluids

    public static final RegistryObject<ForgeFlowingFluid> LIQUID_SUGAR_FLUID_SOURCE = register("liquid_sugar_fluid_source", LiquidSugar.Source::new);
    public static final RegistryObject<ForgeFlowingFluid> LIQUID_SUGAR_FLUID_FLOW = register("liquid_sugar_fluid_flow", LiquidSugar.Flowing::new);

The registering of the Sourceblock

    public static final RegistryObject<LiquidBlock> LIQUID_SUGAR_BLOCK = BLOCKS.register("liquid_sugar_block",
            () -> new LiquidSugarFluidBlock(ModFluids.LIQUID_SUGAR_FLUID_SOURCE, BlockBehaviour.Properties.copy(Blocks.WATER).randomTicks().noLootTable()));

 

Now i tried adding randomTicks (i want the fluid to change blocks around it) but i cannot seem to get it to work:

@Override
    public void randomTick(Level pLevel, BlockPos pPos, FluidState pState, RandomSource pRandom)
    {
        DevUtil.outputDevMessage("randomTick0");
        if(!pLevel.isClientSide())
        {
            DevUtil.outputDevMessage("randomTick1");
            for (int x = RADIUS; x >= -RADIUS; x -= 1)
            {
                for (int y = RADIUS; y >= -RADIUS; y -= 1)
                {
                    for (int z = RADIUS; z >= -RADIUS; z -= 1)
                    {
                        if ((Math.abs(x * x) + Math.abs(y * y) + Math.abs(z * z)) <= (RADIUS * RADIUS) + RADIUS)
                        {
                            DevUtil.outputDevMessage("randomTick2");
                            BlockPos pos = pPos.offset(x, y, z);
                            BlockState state = pLevel.getBlockState(pos);
                            changeBlock(pLevel, pos, state);
                        }
                    }
                }
            }
        }
    }

To test why it doesnt work i added those outputDevMessage calls. They work in other functions that are called, but not in this one. So i assume that the randomTicks are not called at all.

I had this randomTick method in the Block class of the fluid as well as in the liquid class, no sucess with both.

 

Anyone know what i'm doing wrong?

Okay, i went a little bit further down the rabbit hole.. For the randomtick method to be called in the serverlevel.java it needs to check the fluidstate.isRandomlyTicking():

FluidState fluidstate = blockstate2.getFluidState();
                  if (fluidstate.isRandomlyTicking()) {
                     fluidstate.randomTick(this, blockpos3, this.random);
                  }

This is calling the isRandomlyTicking() method of the fluid that is associated (Fluidstate.java):

public boolean isRandomlyTicking() {
      return this.getType().isRandomlyTicking();
   }

Now here comes the problem. The Fluid.java isRandomlyTicking method is always returning false, no matter the properties you gave it. So yeah, after overwriting that method it works now.