The Emperor's Other Clothes

While the Emperor tetra has been a popular aquarium fish for several decades, it has a close cousin whose gorgeous glittering colours arguably should have made it the favourite of the family…

- Keith Naitby

Hands up, how many of you have kept Emperor tetras? Not bad, not bad, that’s quite a few. Now if I asked the same question regarding Rainbow tetras, I suspect there’s a decent percentage who have never heard of them, let alone seen one. In one of those strange anomalies the world of fishkeeping has a habit of producing, one fish has found worldwide acclaim, while a close cousin is largely ignored. Such is the case with Emperor and Rainbow tetras. Although both species of this Nematobrycon genus are suited to aquarium life, the one we most rarely encounter is arguably the more beautiful.

Setting the stage

I have to admit, designing a tank to show offRainbow tetras to their absolute zenith is a tricky proposition. The key appears to be a balance between their natural environment, our aesthetic desires and where your tank is situated.

Just like the familiar Emperor tetra, these fish are indigenous to the soft acidic waters of Columbia. To replicate these conditions in the aquarium, a mixture of RO and tapwater will create the ideal parameters with a pH around 6.5 and 4°H. Tank bred fish can tolerate something a little harder and slightly alkaline but wild imports need to be housed in the appropriate water. I would include some terrestrial leaf material in the form of oak or Catappa as this will give them a taste of home with the gentle release of tannins. In terms of substrate, a dark base seems to blend nicely with the deeper pigments on these fish.

Blast Rainbows from above with anything beyond a single light tube and the lovely, now you see me, now you don’t apparel will simply be washed away. I like to view Rainbow tetras against a background of greenery but plant choice has to be tuned to the toned down illumination that best suits these fish — Cryptocoryne with their variety of size and shade are a good choice.

Lighting up the Rainbow