NOTE: this was posted by faygosgurl_888 on Sat, 04/23/2011 - 17:50, but somehow it ended up in the Cat Forum under "Behavior" and was entitled "Betta Behavior".
I felt the person who responded to "faygosgurl_888" did such a good job of responding that I wanted to "re-post" it here so others could benefit.
Here is the QUESTION by "faygosgurl_888" -
Weve had our betta for 6 or so months now and hes had other fish and even shrimp in his tank, but others died off so it was just him for awhile but then we got more shrimp. We put two in and next thing you know they died. Ever since everytime someone walks by or we turn the light on he shoots from side to side hiting the sides of the tank and hes been chilling at the bottom of the tank. WHATS WRONG WITH HIM?
Here is the RESPONSE by "PetSmart_Admin" -
There are several concerns with your comments. It is important to understand that Bettas are air breathing fish. They have a Labyrinthine organ that functions like a lung. Because of this, they can live in a bowl without aeration or water circulation. Other species of fish require oxygen from the water, and so they need an aquarium with aeration, and will die if kept in a bowl without aeration and filtration. Unless you are keeping your Betta in an aquarium with aeration, you will not be able to put any other fish with them. The shrimp also require oxygen in the water, but they are more tolerant of low oxygen conditions than fish. Another possibility for their dying may be poor water quality. Without filtration, the water needs to be changed weekly with dechlorinated water. You can test your water with aquarium test strips to check the water quality, or PetSmart stores offer free water quality analysis if you bring a water sample into the store.
You second comment about him hitting the sides of the tank indicate that the tank size may be too small for him. Bettas are sedentary fish, often sitting on the bottom of the tank or nestled in branches of aquatic plants. They are predators that wait for food to swim by then attack. They are not active swimmers like most species of fish. When a noise, or bright lights or motion startles them, they react by rapid swimming. In a small container that can be a problem if they have not much room.
If you are interested in more fish than just one Betta, you may be interested in getting a bigger aquarium with adequate filtration so you can keep multiple fish and shrimp together successfully. See the Care Guides on setting up an aquarium and on the fish species that are available at PetSmart stores. These Care Guides are free at the stores, or can be seen on PetSmart.com/careguides.
(Of note - here is the link to the original posting: