Fish Bowl
If you choose to keep fish in a bowl, there are several things you should keep in mind. Fish kept in bowl will continue to produce waste as they consume food, and any excess food that gets into their tank will still begin to decay. Decaying food, fish waste, and debris that falls into the tank from the air will all contribute to poor water quality, and can eventually reach toxic levels. In a small environment like a bowl, this problem is compounded by the small volume of the water. In larger environments, there is more water to dissipate these toxins.
Keep the water in your fish bowl low. The water level should be near the widest part of the bowl to optimize the surface area where Carbon Dioxide can be released into the atmosphere and Oxygen can be dissolved into the water. Remember that lowering the water level also decreases the water volume in the bowl, thereby decreasing the ability of the water to dissipate fish waste and other toxins and lowering the fish capacity of the bowl.
Fish Bowl Capacity
Possibly the most frustrating thing about owning a fish bowl is the limited capacity for fish. In a filtered bowl, we recommend keeping only 1" of fish for every 1.5-2 gallons of water in the bowl—remember that the bowl is probably holding substantially less water than its total capacity since you are keeping the water level lowered to the widest part of the bowl—usually 1/3-1/2 of the bowl's capacity is air, not water. If you are not filtering your bowl, we recommend keeping your population at 1" of fish for every 3 gallons of water or lower. Remember that a fish's size is not determined by the environment it is kept in, but rather is controlled by genetics. The small fish you purchase for your bowl today may be a very large fish by the time it is mature. Keeping a fish in an environment that is too crowded or too small is cruel and can lead to a wide variety of health problems from reduced immune systems to crippling skeletal deformities or failure of internal systems
