This Aquarium Answers Post is simply for fish fin and fish anatomy identification.
The pictures can apply to most fish kept in freshwater and saltwater with the exception of Sharks, Rays, and Skate.

The first picture is of the anatomy of a bony fish (an Oscar).


Details include:
*Brain: Center of mental faculties of a fish.
*Esophagus: Part of the digestive tract connecting the mouth to the stomach.
*Dorsal aorta: Vessel in the back that carries blood from the heart to the organs.
*Stomach: part of the digestive tract between the esophagus and the intestine.
*Air bladder: Organ that regulates buoyancy in the water.
*Spinal cord: Nervous system part that connects the brain to the rest of the fish’ body
*Kidney: Blood-purifying organ. Common site for infections including dropsy
*Urinary orifice: Opening for urine elimination
*Genital Orifice: opening related to the genital organs.
*Anus: end of the digestive tract.
*Gonad: hormone-secreting sexual gland of a fish.
*Intestine: final stage of the digestive tract.
*Gall bladder: Small sac containing the bile for digestion
*Liver: Bile-producing digestive gland.
*Heart: Blood circulatory organ.
*Gills: Respiratory organ of a fish.
*Eye: Fish sight organ
*Olfactory bulb: Prominent part of the smell organ of smell of a fish.
*Pyloric cecum: Dead end related to the intestine.

The second Picture is of the names of fish fins and lateral line also using an Oscar (Cichlid).



This includes:
*Pectoral fin
*Anal Fin
*Pelvic Fin
*Caudal Fin (tail)
*Dorsal Fin
*Lateral Line
*Nasal Opening
*Vent (anus)

Here is a picture of a Catfish for an example of adipose fins and barbels: