Koi can Hear: Carp and Koi have some improvements to their hearing system that improve the range of sounds
they can hear.
Most fish cannot hear frequencies above 1,000 hertz, but Koi can hear 3 times higher, up to 3,000 hertz.
The reason for this is Koi have a type of amplifying system called the Weberian Apparatus that other fish do not
have. It consists of 4 pairs of bones called ossicles, which form a linkage connecting the inner ear to the swim
bladder. This connection of the swim bladder's air chamber to the inner ear greatly improves the Koi's ability to
hear.

There are 3 pairs of otoliths or ear stones in the inner ear of a Koi. The largest pair of Otoliths, the sagittae, are
routinely used for aging. So Otolith is synonymous with sagitta.
Humans have otoliths too, but our hearing system is much more advanced than Koi.

Koi can Taste: They have taste buds almost everywhere:
- On their lips
- Within their mouth cavity
- Their fleshy barbels (2 in each corner of the mouth) bear numerous taste buds and are highly sensitive to touch
- Most of their bodies are covered with innumerable taste buds, including their fins and tail

Koi can Smell: The lining of the olfactory or nasal organ in Koi has special sensory cells to function as smell
receptors.

Koi can Blush: Koi show stress by blushing red in their fins and on their bodies. When they are handled in a
net you can see the red in their fins, between the spines. Also when they are in a stressful environment, such as
bad water, they will often show a red blush on their bodies under the scales. Sometimes they almost look like they
have varicose veins.
You can see the red in the front spines of the dorsal fin, and on the caudal fin.
If you see this they are trying to tell you something is causing them stress. Take measures to relieve the stress or
you will start to lose Koi.
This is similar to when we blush from embarrassment or stress.