The Ultimate Fluid Tank is a machine added by Mekanism, which serves as a storage for any type of fluid (e.g., Water, Lava or the fluids from Mekanism). It is the fourth tier of Mekanism fluid tanks.
The tank stores a maximum amount of 112,000 mB and can be filled via Bucket or connected fluid pipes (e.g., the Basic Mechanical Pipe). The player can insert or extract liquids by right-clicking with a full or empty bucket respectively on the tank. The same can also be done via GUI, where the filling level is also displayed. In addition, storage items from other mods also work, such as the Universal Fluid Cell from IndustrialCraft 2.