A red aro kept indoors away from sunlight develops the red at a very slow pace. Tanning is a way to introduce uv into the tank for the red to progress into colouration as it would under "normal circumstances" in a pond environment.
In a tank condition, a red does not colour up well without the uv exposure.
This is different from hobbyists using a special light which makes the red appear redder than it is, what we have in Singapore are "Nan" lights. I think we need to be clear about this before the discussion can go anywhere. If we view tanning positively, it is to replicate the natural environment by giving "sunlight" to the fish to enhance it's development.
The Arcadia arowana lamp is newly introduced into the hobby just about a year or so in Singapore. Before, hobbyists were using PL lights (fluorescent), T5 (also fluorescent), "Nan" lights which doesn't seem to do the job of tanning well enough. Any form of light would have some of the uvb, but the Arcadia has more of it, hence it is considered a most appropriate lamp for tanning.
There is some truth that colour only comes with maturity, and a red matures at 7 years plus. It is noticed that way before this, reds do colour up for a season, therefore for many hobbyists, a tanning regime is started just about when the fish starts to turn a year old with blushes showing on it's opperculum (what they call "cracks in the cheek"). You don't need to wait for 7 years at all to see the red in an arowana. In this hobby, some reds colour up faster than others, this has to do with the genes more than anything else. Nevertheless, all reds do improve in colouration when they are put under a tanning regime.
To do this humanely, a few hours of tanning is adequate, with the help of a timer plug this can be achieved. 5 hours a day is a pretty good guide, at max 8 hours since it mirrors the daylight hours in a pond. I think it is only a cruel practice if the tanning is done 24X7 because it deprives the fish of sleep.
Tanning is best introduced slowly, starting with two hours, and upwards, watching the reaction of the fish.
If the fish reacts negatively, such as refusing food, swimming at an angle, it's best to withdraw and start again later. When an aro swims at an angle, it is a dangerous sign because the tilting posture can bring on "dropped eye" which is a condition whereby the aro lowers its field of vision so that the eyes appear drooped all the time. Do be careful of this and early correction is necessary.
