Highest Watt Light Bulb a Fish Can Withstand

Lighting is critical to certain aquarium setups. While it's possible to injure a fish's eyes with too powerful lighting, it's unlikely that you would encounter this problem without something else going wrong in the aquarium first, and it would be difficult -- and even expensive -- to reach this point with most aquariums.

  1. Highest

    • Most aquarium fish come from the tropics, a region where the sun's light is stronger than anywhere else on the planet. In saltwater aquariums that feature corals, more than 5 watts of lighting power per gallon is routinely recommended for aquariums that feature both fish and coral. Most aquarium fish have adapted to environments with very powerful light. As long as the lights aren't blinding you when you look at the aquarium and the aquarium is not overheating, the fish are most likely fine.

    Typical

    • No fish really have a minimum amount of light that they need to thrive. For most aquariums, 1 watt per gallon of lighting power is sufficient to illuminate the fish. For aquariums larger than 30 gallons, you may want to step up to 2 watts per gallon. In short, you only need enough light to see the fish to keep them happy. However, many aquariums also feature live plants and coral. These organisms need more light than this to survive.

    Problems With Light

    • Light can cause some problems. Some fish, even some tropical species, come from well-shaded rainforest rivers. For these species, too much light can stress them out and make them skittish. You can try adding plants to the tank to provide them with darker, shaded areas. Additionally, if your lights are too powerful, and you have no live plants, they can encourage algae blooms. You can control this by putting the lights on an outlet timer, and limiting the aquarium to 8 hours of supplemental light per day.

    Spawning

    • One special case is when fish spawn. Some river fish are very sensitive to light, and changes in light, when they're spawning. Use dim light, possibly no lighting beyond the room's light, for such fish. For some South American tetra species, you may have to go as far as to cover the aquarium in cardboard to block out ambient light if you want to spawn them.