The Ultimate Planted Tank Lighting Guide

Start with 6-8 hours per day. Most planted tanks thrive at 7-8 hours. New setups should begin at 6 hours to prevent algae while plants establish, then gradually increase. Advanced tanks with CO2 injection and balanced nutrients can run 8-10 hours. Never exceed 12 hours — algae will inevitably take over. Use a timer for consistency; even 30 minutes of inconsistency can trigger algae blooms.

Lumens measure brightness as perceived by human eyes — useful for room lighting but meaningless for plants. PAR (Photosynthetically Active Radiation) measures the light wavelengths plants actually use for photosynthesis (400-700nm). A 3000-lumen light could deliver less usable PAR than a 1500-lumen light designed for plants. Always shop by PAR values, not lumens or watts. Look for lights that publish PAR data at various depths.

Technically yes — plants don't know where the light comes from. But regular LED bulbs lack the proper spectrum balance (they're weak in red and blue peaks), have poor water penetration, and aren't designed for the humidity above a tank. You'll get slow, leggy growth and dull plant colors. Dedicated aquarium LEDs have spectral tuning, IP ratings for moisture, and mounting systems designed for tanks. For a nano tank under 5 gallons, a 6500K household LED bulb can work. For anything larger, invest in proper aquarium lighting.

Yellowing (chlorosis) usually means a nutrient deficiency, not a lighting problem. Common culprits: iron deficiency (new leaves yellow, veins stay green), nitrogen deficiency (old leaves yellow uniformly), or magnesium deficiency (patchy yellowing between veins). Good lighting actually increases nutrient demand — more light means faster growth means plants consume nutrients faster. If you recently upgraded your lights and plants started yellowing, you likely need to increase fertilizer dosing to match the new growth rate.

It's a nice-to-have, not a necessity. Fish appreciate gradual light changes (helps prevent startling), and it adds a premium feel to your setup. But plants don't benefit significantly — they begin photosynthesizing as soon as light hits their leaves. The ramp-up time shouldn't count toward your photoperiod: if you ramp up for 30 minutes and run full light for 7 hours, that's a 7-hour photoperiod. If your light has the feature, use it for the natural aesthetic. If it doesn't, don't worry — your plants won't care.

Algae is your first warning sign — green dust algae on glass, hair algae on plants, or persistent green water all point to excessive light. Other signs: plants that look pale/bleached (photoinhibition), fish hiding more than usual, or rapid evaporation. Quick fix: reduce photoperiod by 1-2 hours or raise the light fixture 2-4 inches higher. If you have adjustable intensity, dim to 70% and observe for two weeks. A PAR meter is the definitive answer — if you're hitting 80+ PAR at the substrate with no CO2 injection, that's too much light.