Aquarium lighting is the second-most-important equipment after filtration. Good lighting drives plant or coral growth, color expression, and fish behavior; bad lighting starves photosynthetic livestock or feeds algae instead. Modern reef and planted-tank LEDs have replaced T5 fluorescent and metal halide as the standard.
Freshwater fish-only: 30-40 PAR is sufficient. Planted low-tech: 30-50 PAR. Planted high-tech: 100-150+ PAR with CO2. Reef softie / LPS: 100-200 PAR. Reef SPS: 200-450 PAR depending on species.
Reef tanks need heavy 420-460nm royal blue plus 380nm violet. Planted tanks need full-spectrum 6500K white with red 660nm peak. Fish-only freshwater can use any reasonable LED spectrum without spectrum-specific concerns.
Nano (under 30 gal): AI Prime 16HD, Reef Brite XHO. Mid (30-65 gal): AI Hydra HD26, Radion XR15. Larger (75+ gal): Radion XR30, multiple Hydra HD52, or T5 hybrid (T5 + LED point source). $200-1500 depending on tank size.
Twinstar 600S/900S, Chihiros WRGB II/Pro, Fluval Plant 3.0, NICREW SkyLED Pro. Look for >100 PAR at substrate for high-tech setups. $100-400 depending on length.
Aquaclear, Fluval Aquasky, Hygger, NICREW. Most $30-100 LEDs work for fish-only or low-light plant setups.
Start at 6 hours of full output, increase to 8-10 hours over 4-6 weeks. Use a 30-minute ramp-up and ramp-down. Longer photoperiods favor algae growth over coral/plant growth in unbalanced systems.