Lighting doesn’t make sense for a simple betta bowl. Some people do put their betta bowls under table lamps, or use clamp lights. If you want to add a light, that’s fine. The only need for it would be if you have plants that require brighter light that indirect sunlight. Amazon swords, for example, will need extra light, as will many vallsineras.
If you bought a java fern or java moss for your betta bowl/aquarium, you’ll probably be fine with just indirect sunlight. Java ferns and java moss are widely considered the best plants for bettas. Some betta breeders consider java moss an essential item in the breeding and fry-raising tanks. The java moss gives the female betta a place to hide, and later it does the same for the small fry. They can also eat bits of the java moss, which takes one wee bit of that part of the job off you.
For those of us who want just a simple, low to no-tech betta bowl, natural sunlight is the best choice. While it is tempting, do NOT put your betta bowl or tank in direct sunlight. The sun will overheat the bowl during the day, and then at night your betta’s water will have a severe temperature drop. Big hikes and drops in water temperature are even harder on bettas than just being cold all the time.
Direct sunlight also seems to make many bettas really twitchy behaviorally. This does make sense – they evolved to live in ditches and to hide, so they are not used to open water in full sun, but that really is only half an explanation. I don’t know the full explanation of why full sunlight stresses bettas, but it does. Keep your betta out of full sunlight.
Nice indirect sunlight is fine, though. In this sense bettas are a wee bit like ficus trees. Ficus trees can not handle direct sunlight (it burns their leaves) but they do need a fair amount of light. Bright, indirect sunlight is good. My betta, Charlie, is in a bowl that gets bright direct sunlight. There’s an amazon sword plant in his bowl (an eclipse hex 5) that is growing better than plants I used to keep under expensive aquarium plant lights. Of course, we do have algae issues (you put a bowl in even medium sunlight and it will grow algae), so I got a snail, and when I change the water in his tank I swab the inside side down with a paper towel or two. So the algae is under control, and the plant looks great.
If you have a full-scale community tank, complete with a cover, you will need some lighting, even if your tank is next to a bright window during the day. Flourscent bulbs with a plant-friendly full spectrum are an excellent choice. Metal halides are for serious fishkeepers who want to do aquascaping. A good quality fluorescent bulb will cost around $20; metal halide setups start in the hundreds of dollars.
Get yourself a nice cover for your aquarium that will accommodate not one, but two rows of lights, buy good quality flourscents, and you’ll probably be OK with most medium light plants. If you get a glass cover for your tank, you’ll also be able to add another strip of flourescents later if you want to increase the light.
Aim for about two watts of light per gallon of aquarium water and you’ll have nice lush growth in your medium light plants. Do be sure to ask before you buy plants if they require high light, then if they do, pass on that plant. Leave it to the people with the expensive metal halide setups.
