The sizes of the frames (with "frames" I mean the thin lines that appear when you hover your mouse over a block, on its edges) of the corals (not the Coral Blocks, just the Corals), are inconsistent in size and alignment respectively to the coral's space bounds (in other words, occupying space from the block's space next to it, out of its own bounds).

The alignment issue, is noticiable in all normal Corals, specially in the Tube Coral, where the frame goes out of the bounds of its space (unlike the other Corals, which just are unaligned).

The size issue, is noticiable in the Coral Fans, where the frame isn't covering the whole coral, just the center, besides the Tube, Brain, and Fire Corals.

Hope this little information helps.