The Fluidic Nether Portal is a tank added by Engineer's Toolbox. Putting a Fluidic Nether Portal in the Overworld will make one appear at the corresponding spot in the Nether (dividing the Overworld portal's X and Y coordinates by 8, due to Nether properties). They are linked; any liquid put in one will be in the other with the same amount. However, if one is destroyed, the other is also destroyed. They are like the same tank block, but in two dimensions at once.
The Fluidic Nether Portal has 8,000 mB of fluid storage. It can be configured to not accept Lava into it, since its presence in the Nether enables easy Lava-powered energy production.
The Fluidic Nether Portal can only be placed in the Overworld. It will not be able to be placed in the Nether or The End.