Day-Night Cycle
Bettas need 8-10 hours of light per day, then full darkness at night. Use a timer — irregular lighting confuses circadian rhythm and stresses the fish.
Avoid leaving room lights on at night. Cover the tank or move it away from TV/monitor light if needed. Bettas sleep deeply and benefit from real darkness.
Light Intensity
For a fish-only tank without plants: low to medium intensity is ideal. Bright lights wash out color and stress wild-caught bettas especially.
For a planted tank: intensity depends on plant needs. Low-light plants (java fern, anubias, mosses) only need 20 PAR; high-light plants (carpet plants, red plants) need 60+ PAR with CO2.
- ✦Add floating plants for natural shade.
- ✦Dim the light during morning/evening for a sunrise/sunset effect.
Best Light Fixtures
Nicrew Classic LED (budget), Finnex Stingray (low-light planted), Fluval 3.0 Plant (high-light with full programmability) are the go-to choices for nano betta tanks. Avoid generic clip-on lights with no spectrum specs — they often cause algae.
Algae and Light
Excess light causes algae. If green algae coats glass within a week, reduce photoperiod by 1-2 hours. Brown diatom algae in new tanks is normal and clears as the tank matures.