Is it not possible to put RC tanks next to each other? I was pretty sure I'd seen in a YT video someone with a room full of them all touching each other, with different liquids in each ??? It doesn't seem to matter what I try, as soon as I place a tank block next to my existing tank it shows the tank as incomplete. Is there some trick I'm missing or do you have to leave a block space between them?
I should add that these tanks are for different liquid tanks.
Railcraft multiblocks cannot touch each other; it's the same with coke ovens and so on.
However, newer Railcraft versions add a lot of decorative blocks that imitate the multiblock structures. For example, you can make a kind of brick that looks exactly like the coke oven bricks, except that it's purely decorative. Those blocks can be used to close gaps between coke ovens, or build them seamlessly into larger structures, without disrupting the multiblocks.
Who knows, maybe there is such a decorative block for iron tanks as well?
Also, are you sure that the person in the video was using Railcraft tanks, and not Xycraft ones? Those are able to touch each other...