For about $6 you can take a betta fish home, and while they are one of the easiest fish ever to take care of (even easier than goldfish), there are a couple of things you should know to keep yours not just alive, but looking good and staying active.
1) At least a one gallon bowl. Two gallons is much better.
Do not listen to the pet store people about how a betta fish can live in a little cup of water. They want to sell you a new one in two months when your current one dies. They don’t really care if your fish looks terrible between now and then. Keeping a betta in a tiny “betta bowl” will also mean that you will need to change the water almost every day. If you keep it in a two gallon tank, you can get away with changing the water twice a week, and if you get a three gallon bowl or larger, you’ll be able to change it only once a week.
Another problem with having a betta in such a tiny bowl is that their water temperature can rise and fall dramatically between day and night. This will stress your fish a lot and make it much easier for your betta to get sick. Then you will need to buy $10 or more fish medication. So get a good sized bowl, please. Even a globe flower vase will do.
2) One betta to a bowl.
The pet store will probably tell you this, but do not put more than one betta to a bowl. Even females and males will not get along. One will attack the other until its fins are shredded and it dies of stress a few days later.
3) Bettas need to be warm.
Betta fish need water that is around 75 to 80 degrees. That may be easy during the summer, but during the winter, and especially at night, your betta is going to need extra heat. Otherwise they will get sick, look awful, make you feel bad and then cost you $10 or more for that fish medication, which may or may not save your fish.
If you do not want to use the classic tube heaters, there are rubber-covered flaps that will heat five and ten gallon tanks. They cost about $8. Or, if you have one, you can put your betta on a seedling heat pad. These heat sources are waterproof and give out very low heat, so there’s no risk of overheating the betta or of burning yourself (or your children, if it is their fish).
4) Do not overfeed your betta.
Bettas should be fed once a day. Do not feed them one day a week to keep them in optimal condition. In fact, if you want to go away for 3-4 days, you betta will be fine for that long. If you happen to have a live plant in their bowl, they will pick at the plant, but even without it they will be fine.
How much to feed your betta? Well, not much more than the size of their eye. That is about how big their stomach is. Just in case you were wondering: Overfeeding makes more bettas sick than anything besides bad water.
5) Skip the “betta water” at the pet store
Get yourself a little bottle of betta water conditioner, or any general water conditioner for aquariums. The $5 you will spend for the water conditioner will create the same amount as $200 worth of “betta water”. You can use tap water for your betta, just follow the instructions for the water conditioner. I like to keep 2-3 gallon jugs of treated tap water available for water changes.
You must do those water changes. Even if you just pour out half to two-thirds of the water, then pour in your pre-treated water, that is a lot better than nothing, and it will take less than two minutes.