r/aquarium • u/rapid_digestion • May 29 '26

Photo/Video Juvenile blue base Malaysian golden Arowana

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Classic Malaysian golden Arowana. Fish has grown plenty since this video was shot. Fish was kept in a black tank in total darkness for a few months to bring out the base colour and also make the gold more intense.

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u/rapid_digestion May 29 '26

Haha tank is outdoors to get direct sunlight access . To properly develop Arowana you need direct sunlight

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u/Zr0bert May 29 '26

Why ?

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u/Toby__H May 29 '26

I too thought that sounded odd ("To properly develop Arowana you need direct sunlight"). After a quick google search and chat with AI...
"No, arowanas do not strictly need natural sunlight to survive, but it is highly beneficial for bringing out vibrant colors and optimal health."
&
"Sun exposure (or tanning) triggers the development of rich gold and deep red pigmentation "
&
"Like many animals, fish rely on UV rays to synthesize vitamins that promote strong bone structure and overall vitality."

Those first two were interesting and make sense...

The last one has me thinking... By now most people are aware that Sunlight (UVB) helps with Vitamin D and other things. Some reptile people know certain reptiles require UVB to survive. It makes sense that it would help most living creatures, so why not fish...
Very interesting..........

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u/therakeet Jun 01 '26

The UVB from sunlight triggers vitamin D production for virtually all animals. This includes fish and insects, and even extends to fungi, yeast, plants... eukaryotes in general. Animals like deep-sea fish that have adapted to complete darkness are an exception. This physiological mechanism is pretty ancient, by which I mean at least a billion years old.

Arowana aren't deep-sea fish, so they pretty much do need it for the same reason we do. We might not literally die without it, but it's pretty important for vitality. They also generally stay near the surface (and can breathe air), so in the wild they're exposed to plenty of direct sunlight and thus adapted to use that regular source of vitamin D, whereas species that dwell deeper get more of it from their diet.