Red Blue Peru Tetra

February 18, 2020March 10, 2023 Jeremy Gay

Two years ago I got to keep one of my bucket list Characins – Hyphessobrycon sp.”Red/blue Peru”, now properly described and named Hyphessobrycon margitae. But why did it make my bucket list, and who is Margit?

Firstly my fascination with this tetra has to be because of its looks. On a bad day, with squinted eyes, you could be forgiven for walking past them in the shop and thinking they were a Black neon tetra, but catch it on a good day, in your home, furnished aquarium and Red/blue Peru is a definite contender for one of the most beautiful of all tetras.

It is like a Black neon tetra in shape and size, but that black horizontal band is overlaid with iridescent scales which flash, light blue, Indigo or violet depending on how the light catches it. On the top of the caudal peduncle is a gold flash, with the black band extended into the tail fin. But the real party piece is when the males turn on the bright crimson colour in their pectoral, ventral, anal and tail fins to show off to passing females.

The hunt

Practical Fishkeeping Magazine has a particularly good photograph of one such male fish which has haunted me ever since I laid eyes on it. The specimen was perfect and the camera flash exquisitely captured that iridescent overlaying sheen. That sparked what must have been a ten-year search and in that time I only saw them perhaps ten times in the shops, and that was based on a career which took me to most of the aquatic stores in the country.

For one reason or another, the timing or budget was never right until that year, when I set up a planted tank with no clear conceptions of what I would stock it with. My usual Saturday scouring of my local fish shops, family in tow led me (knowingly,) to a store which had flashed some up on their Facebook page that week. As per usual I scanned every tank from top to bottom, searching each one for fishy delights and speed reading every label. I tried to look disinterested for the family’s sake, and make out I’d just stumbled upon the fish section of this store after an accidental twenty mile trip out in the car.

Then there they were – at eye level – for all to see. I checked the label. “Red/Blue Peru”. I had a quick count. Seven or eight. That will do nicely. I re-read the label, checked the price, then re-read the price. £4.95, that’s half what I’d seen them on sale for before. Severn or eight times £4.95. Even I could afford that. The heartbeat started to race. I checked the competition, meaning I did a quick recce of who else was in the shop. I reckon there were another half a dozen or more ~~competitors~~ customers in eyeball reach of my prize, and two of them were right next to me.

What if they want them? I thought. What if they want them, have seen them and one of them has already gone up to the counter to ask for them? I spread my body wide to try and block the fish from view. I nearly put my arms out and shouted mine. Then before I knew it I was walking to the counter. The kids weren’t big enough to hold guard over the tank so I had to move fast. They could look after themselves for a second or two though. Their mum would be around somewhere…

“Those Red/blue Peru, I panted, with pupils dilating. Yes…said the store manager. “How many are there?” I asked in Dopamine induced monotone. “There were ten, he said, “Yes I think there are ten. “How much are they I asked,” knowing full well. “£4.95,” he said. “Would you…like them?” “Yes, yeah I think I’ll take the lot please,” I said, with my head and body already turned and marching straight back to my fish.

To give you an idea of how much these fish can turn their colour and dark stripe on and off, the two of us struggled to find all ten fish in a bare two foot tank with handfuls of other community species. I paid, got 10% off, (well just because,) and drove them home to float my prize.

Home and well

Since moving oop North I am blessed with soft water, so the chances of me ending up with tetras were premeditated. I released my ten Red/blue Peru into my three-foot planted tank with eight Pretty tetras, Hemigrammus pulcher, for company. Conditions were obviously to their liking as within hours, that afternoon, the first male displayed pleasure for his new dwelling by turning on the colour.

From plain, generic Hyphessobrycon came bright red fins as he took centre stage. In a clearing, halfway off the bottom and two-thirds of the way across the tank he started to dance. With fins so stiff and erect he looked like he had been electrocuted, the male circled over a diameter of about eight inches, circling, first clockwise then anticlockwise, kiting left then right as he did so. My face up close against the glass I observed my new possessions, their pretty faces and visible, but tiny teeth. I was a happy man indeed with my addiction well and truly fuelled.

Feisty fish

The next day a couple more males coloured up, deliberately catching the gaze of the first, Alpha male. Fins flew as they clashed repeatedly, darting at each other at lightning speed, flaring, flashing and sparring. Females got involved then too, also fighting with the in-colour males, trying to make a space of their own or being chased out of one of several male territories.

By Monday, after work, I came home to find my beautiful, placid Pretty tetras huddled by some plants in the rear corner. The Red/blue Peru had carved the tank up like a group of Malawi cichlids! Were these a super feisty species I pondered or are all tetras like this, only completely overshadowed in almost every aquarium by more boisterous tankmates? Fascinating to watch the behaviour though, and I’m guilty of writing-off many tetras as boring over the years. I was now thoroughly back in love them…

I had split fins in both males and females by now, the males were so hormonally charged that they weren’t even feeding and constant fighting was starting to make them look thin. A few days later and the inevitable Whitespot hit these newly imported fish. I turned the temperature up to 28C to speed up the parasite’s lifecycle. The fish stopped fighting, although I took this as a sign of discomfort at the warm water. My thoughts went to my shrimp too, who were conspicuously high up in the vegetation for a change, so the next day I started a course of Whitespot treatment, turned the temperature down to 26C and the disease went away. As soon as the temperature was lowered the feisty behaviour returned.

Weeks on and the fish were calmer, more spread out, and I was still loving them. After several Google searches I’m not sure that there aren’t several species which have been sold as sp.Red/Blue Peru over the years. Several common names too including Bleeding blue and Imperial blue rainbow tetra, although now the Imperial moniker seems more attached to H.nigricinctus. Mine look identical to some image searches but quite different to fish in others. And like Neon and Cardinal tetras that light refraction definitely makes the fish look a completely different colour depending on if you are viewing the fish from below, straight on, or above.

Have they bred? I’d like to think they have spawned, but I haven’t made a conscious effort to try and breed them so far. Long term I may separate the Pretties and the Red/Blues. The Pretties are now much more used to them and the odd daring male Pretty tetra will even colour up and carve out his own eight-inch diameter circular clearing on occasion, but I aim to offer the Red/Blues a larger tank, perhaps a 5×2’ planted tank one day, with lots of space for them to spread out and get out of each other’s way when they want or need to.

So why are they now called H.margitae? The “ae” at the end of the specific name is a clue that it is named after a female, and once I posed the question on the most excellent facebook page “Characins of the World,” I got a reply from Pete Liptrot of Bolton Museum Aquarium. “It’s not H.margaritae, it’s margitae, after the author’s wife, Margit Zarske.” Said Pete. Further investigation then took me to Mr Axel Zarske, a prolific German ichthyologist who has described many fish including some beautiful tetras and the now mainstream H.amapaensis. So H.sp.Red/Blue Peru is no more and it is now officially called Hyphessobrycon margitae, named after Margit Zarske, the wife of Axel Zarske. And for those who like an accurate biotope, the paper describing the species revealed that it comes from the Rio Nanay drainage in Peru, also home to some particularly nice Angelfish showing red and blue colouration. Now that would be a nice biotope tank!