Aquarium Lighting: T5 Lighting Vs. HQI

The inhabitants in an aquarium determine the type of lighting required for optimum aquarium health. T5 lighting is a type of fluorescent light. Halogen quartz iodide (HQI) is a type of metal halide light.

  1. Heat Production

    • HQI lighting produces significantly more heat than T5 lighting. HQI lighting, therefore, requires a cooling mechanism, such as a chiller, to maintain water temperature. T5s do not produce the same level of heat so they do not typically require a chiller.

    Light Production

    • T5s are high output (HO) fluorescent lights. While they put out more light than the normal output (NO) and very high output (VHO) T8s or T12s, the bulb is smaller. This enables you to put more bulbs in a single hood, thereby increasing the overall light production. HQIs, on the other hand, have a small bulb that emits a lot of wattage. You don't need more than one or two bulbs to create sufficient light production, even for light-loving coral.

    Lighting Effects

    • Metal halide lighting, including HQI lighting, is the only aquarium lighting that produces the glimmer effect. You cannot achieve a glimmer effect with T5s even if you use multiple bulbs. The glimmer effect is the shimmering on the tank bottom that mimic shimmering in an ocean environment.