Tadtone

Tadtones are small, many-colored aquatic creatures in Skyward Sword that resemble tadpoles and musical notes.

Collection
Faron releases the Tadtones into Faron Woods after she floods it in order to rid it of monsters who are tainting her realm. Link must collect them in order to prove that he is worthy to receive Faron's portion of the Song of the Hero.

Tadtones appear in six colors - red, yellow, green, cyan, violet, and magenta - denoting their membership in groups of several Tadtones each. Each same-color group of Tadtones corresponds to a sequence of as many notes in the musical score and its members must be collected consecutively before other Tadtones are collected or they will leave Link's inventory and must be collected again. Members of a given group of Tadtones are generally found close together. This behaviour is useful for catching multiple Tadtones at a time by using the spin maneuver to pull them toward Link. The flooded Faron Woods where they are found is the largest and deepest body of water that can be encountered in Skyward Sword and therefore presents the greatest risk of drowning in the game. This is avoidable due to the presence of air bubbles, as in most other bodies of water in Skyward Sword. The Tadtones themselves also replenish air when collected. However, there are also purple bubbles of poison gas that rapidly deplete Link's air meter. In some cases violet Tadtones are camouflaged by being near the poison bubbles. Link must also avoid Blue Chuchus and Froaks, and Craniocs also show up after half of the Tadtones have been collected. Tadtones are said to get along with everyone, meaning they can be found where other fish swim.

It is possible to dowse for Tadtones, although this option only becomes available partway through the challenge after Link has collected a certain number of Tadtones. The ability is gained by talking to Bucha, who will alert Link that he has thought of something useful. Link must stand on the floating vegetation or the top of the Great Tree in order to dowse, though.

Trivia

 * The Tadtones strongly resemble the Zora hatchlings seen in Majora's Mask, both physically and in their gameplay and story role. Along with resembling both tadpoles and musical notes, the Zora hatchlings must also be collected (albeit as eggs) and also form a musical score when they are brought together.
 * Like the Zora hatchlings, they are likely a visual pun on the Japanese word おたまじゃくし (Otamajakushi), which means "tadpole." but can also mean "musical note."