Outdoor Areas +2 Capacity not working with Aquariums?

[unruffled-goat771]

I tried to play a Shark in an aquarium. In theory I had 6 spaces left but the game wouldn't let me put it down. Both Aquariums are touching rocks and should gain +2 Capacity. So I can't see why I can't play my shark. Before I submit this is as a bug can anyone see something wrong?

[Notello]

This plan´s special ability (+2) only applies for standard enclosures. This should be found when hovering over the plan´s description. So aquariums and pet enclosures are not affected.
Those special enclosures have a given amount of spaces to be covered with cubes when placing an animal (when full then full). This plan does not increase these spaces - otherwise the cubes would have to be stacked (in the ftf-version of AN).