Can You Solve this Ice Diamond Riddle? ft. Vsauce’s Michael Stevens

We know that the diamond is small relative to the ice. The ice cube can float only if the diamond volume is less than 4% of the ice volume. It means that the drop of the level predicted by the Boat Puzzle Theorem is hardly noticeable. With the biggest possible diamond, the drop of the level corresponds to about 10% of the ice cube volume. 
In my special troll case,  the diamond is 0.001% of the ice cube volume,  the water is 4°C and it's volume is 20 times the volume of the ice cube,  the ice cube is 0°C, and the water content is insulated. Then the level RISES by a factor of about 2% of the ice cube volume due to the drop of the water density from 4°C to 0°C.