It would be much more convenient to allow the fluid input and output hatches to interact with buckets. Either by right clicking a filled or empty bucket on the hatches, or by having a slot in the GUI that we can place buckets in to empty or fill them. As of right now, we need to use some other mod's tanks and fluid pipes to extract fluid from, or fill up a fluid hatch.

You can rightclick the fluid input hatch with an fluid-container item that has fluid in it to fill the hatch if possible, and you can right-click drain fluid from an output-hatch if the item in hand is a fluid container and there's fluid to be extracted in a form the container in the hand does accept (for example it has to be at least 1 bucket's worth/1000mb before you can extract it with a empty bucket in hand)

If this functionality doesn't work, some mod prevents it or manipulates something so this stops working. It does work indev with a bunch of mods.