The lesson, taught by Derek Muscat, covers various fish species included in the syllabus, focusing on the goldfish, koi, African cichlids, and angelfish. Goldfish are highlighted for their vibrant colors, adaptability to different environments, and peaceful nature, making them a popular choice for home aquariums and exhibits. Koi, known for their ability to control the mosquito population and distinct mustache-like barbels, grow larger than goldfish and require specific conditions for optimal growth, including temperatures between 15 to 25 degrees Celsius.