Goldfish Are fantastic pets with a massive range of varieties out there including the Ranchu, bubble eye, pearl scale and comet. They have been selectively bred for particular traits above hundreds of years, meaning that though 'goldfish' is only one species, you will discover more than 200 subtypes, and goldfish https://www.book-vacuum-science-and-technology.com/flow-of-gases-through-tubes-and-orifices/attachment/3_05/