How to use

BlockFluidBase

in

net.minecraftforge.fluids

public static int getStillFluidLevel(Block block)
{
  return block instanceof BlockFluidBase ? ((BlockFluidBase) block).getMaxRenderHeightMeta() : 0;
}

public static void initPotionFluids() {
  MinecraftForge.EVENT_BUS.register(new PotionFluids());
  for(ResourceLocation registryName : ForgeRegistries.POTION_TYPES.getKeys()) {
    if(registryName.getResourceDomain().equals("minecraft") &&
      registryName.getResourcePath().equals("empty")) continue;
    PotionType potion = ForgeRegistries.POTION_TYPES.getValue(registryName);
    Preconditions.checkNotNull(potion);
    Fluid potionFluid;
    if(potion != PotionTypes.WATER) {
      String fluidName = String.format("potion.%s.%s", registryName.getResourceDomain(), registryName.getResourcePath());
      potionFluid = new Fluid(fluidName, AUTO_GENERATED_FLUID_TEXTURE, AUTO_GENERATED_FLUID_TEXTURE) {
        @Override
        public String getUnlocalizedName() {
          return potion.getNamePrefixed("potion.effect.");
        }
      };
      potionFluid.setColor(GTUtility.convertRGBtoOpaqueRGBA_MC(PotionUtils.getPotionColor(potion)));
      FluidRegistry.registerFluid(potionFluid);
      FluidRegistry.addBucketForFluid(potionFluid);
      BlockFluidBase fluidBlock = new BlockPotionFluid(potionFluid, potion);
      fluidBlock.setRegistryName("fluid." + fluidName);
      MetaBlocks.FLUID_BLOCKS.add(fluidBlock);
    } else {
      potionFluid = FluidRegistry.WATER;
    }
    potionFluidMap.put(potion.getRegistryName(), potionFluid);
  }
}

@SubscribeEvent
@SideOnly(Side.CLIENT)
public static void registerColorHandlerBlocks(ColorHandlerEvent.Block event)
{
  BlockColors blockcolors = event.getBlockColors();
  blockcolors.registerBlockColorHandler((state, worldIn, pos, tintIndex) ->
      worldIn != null && pos != null ? BiomeColorHelper.getGrassColorAtPos(worldIn, pos) : ColorizerGrass.getGrassColor(0.5D, 1.0D),
    BlocksTFC.getAllBlockRockVariants().stream().filter(x -> x.type.isGrass).toArray(BlockRockVariant[]::new));
  blockcolors.registerBlockColorHandler((state, worldIn, pos, tintIndex) -> BlockFarmlandTFC.TINT[state.getValue(BlockFarmlandTFC.MOISTURE)],
    BlocksTFC.getAllBlockRockVariants().stream().filter(x -> x.type == Rock.Type.FARMLAND).toArray(BlockRockVariant[]::new));
  blockcolors.registerBlockColorHandler((state, worldIn, pos, tintIndex) ->
      worldIn != null && pos != null ? BiomeColorHelper.getGrassColorAtPos(worldIn, pos) : ColorizerGrass.getGrassColor(0.5D, 1.0D),
    BlocksTFC.PEAT_GRASS);
  blockcolors.registerBlockColorHandler((state, worldIn, pos, tintIndex) ->
      worldIn != null && pos != null ? BiomeColorHelper.getWaterColorAtPos(worldIn, pos) : 0,
    BlocksTFC.getAllFluidBlocks().stream().filter(x -> x.getDefaultState().getMaterial() == Material.WATER).toArray(BlockFluidBase[]::new));
  blockcolors.registerBlockColorHandler((state, worldIn, pos, tintIndex) ->
      worldIn != null && pos != null ? BiomeColorHelper.getFoliageColorAtPos(worldIn, pos) : ColorizerFoliage.getFoliageColorBasic(),
    BlocksTFC.getAllLeafBlocks().toArray(new Block[0]));
}

event.getToolTip().add("Fluid: " + ((BlockFluidBase) currentBlock).getFluid().getName());

fluidBlock.setRegistryName("fluid." + materialName);
MetaBlocks.FLUID_BLOCKS.add(fluidBlock);