Cardinal Tetras: A School of Beauty, Part 1
Cardinals, Part II

by Alesia Benedict

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If you've read any of my articles over the past couple of years, you know I write on three main subjects: Planted Tanks, Keeping/Breeding Discus, and beautiful Planted Discus Show Tanks. Those three subjects alone give plenty of fodder for readers to contact me with their questions, their problems, and/or their own stories and experiences. Plenty of people have a desire to keep Discus Fish, aquatic plants, or both, so my email box is usually pretty jumping.

The humble Cardinal Tetra really makes a fantastic aquarium guest!  Photo by Robert M. Fenner

I have noticed a very odd phenomenon, however.  Whenever I write about planted Discus show tanks, inevitably I mention Cardinal Tetras (Paracheirodon axelrodi) because most planted Discus show tanks house them. Indeed, all of my show tanks contain cardinals, as they come very close to being my favorite fish (I say "very close" because my passion will always be Discus -- but I also know I would never be happy with JUST a bare tank of Discus fish). One of my favorite things to do in this wonderful hobby is to simply observe my fish.  Geek that I am, I like to just watch them and study their behavior - I never get tired of it, and can literally spend hours in front of my favorite tank, just watching. <Editor's note: I think that we're all geeks!>

The other aspect of the phenomenon that I referred to above is that whenever I mention my Cardinal Tetras in one of my articles, I receive a ton of emails from readers asking me all about the care of this fish! It seems that many readers have a great deal of problem keeping these fish alive for any length of time. Because I have hundreds of these fish, and because I've had them for several years, they are huge and magnificent looking, and I've had readers ask me if they could BUY some of mine.  Of course my answer is always the same - my fish are never for sale!

In my own fish club (North Jersey Aquarium Society), I have fellow members who have been keeping fish for much longer than I have, yet who still have plenty of trouble with Cardinals. One such noted fish keeper says some often die in the bag on the way home from the pet shop, before he can even get them into his tanks! So why do mine prosper and others do so poorly?  I think I know why and would now like to share it with all of you in this two part series.

Cardinal Tetras are often confused with Neon Tetras (Paracheirodon innesi) by newbie hobbyists. While they look alike, they are very different fish with different needs. Neons like cooler water, and are easy to keep and even fairly easy to breed. Indeed, one summer I put some outside on my patio in a tub with some plants and sure enough in the fall when I brought them in, I had many more than my original six!

Cardinal Tetras on the other hand, like warmer water temperatures, which is one of the reason why they are so often teamed up with discus.  They can handle the 82 - 84 degree water, and in nature the two share similar environments. One of the things that is still so amazing about these fish is that nearly all of those offered in pet shops and in our tanks come from the wild. STILL. These little gems seem to be a real challenge to breed and to be honest, I've never even attempted it. Let me tell you why: I was down in Florida doing some native collecting with some of my fish pals and we also toured some of the fish farms there. One of the farms had several tanks where domestic breeding of Cardinals was being done - almost successfully. I say "almost" because while the fishes had indeed bred in captivity, they were SO pale in comparison to what we are used to seeing that they hardly looked like Cardinals. Hence, I figured if this was the best that big commercial breeders could do, maybe I'd stick with just keeping Cardinals! 

Stating that nearly all of the millions of Cardinals we see come from the wild doesn't sound like a big deal, does it?  Consider the following: The fish are typically caught during the "dry season", when the waters are low in the Amazon . Most of the fish are juveniles and as such,  they are quite small. Once caught from their native waters in the jungle, they are brought in buckets over journeys lasting up to several weeks. First, they are brought to the collecting stations of the exporters.  From there, they are air freighted to importers worldwide and then they are distributed by wholesalers to the pet stores. Finally, you and I purchase them for our home tanks, sometimes a month or so after they have been caught! That's why when you see them in your local fish store, they are scrawny and frail looking. Having been fed very little (if at all) throughout the journey, it's a wonder these little guys make it at all.

Okay! So how do we get them into our tanks and keep them long enough to become a magnificent school of darting red and blue?

• Support your local fish store!  If you develop a good rapport with them, they will be honest with you about the condition of the fish. I have gone into my favorite store and said that I wanted to buy some Cardinals.  When the batch isn't up to speed and they are dying quickly, they will tell me "No you don't Alesia". I take my cue and thank them, then try again in another week or two.

• Let the fish stay in the store for a few days, so you don't end up purchasing ones that are on their way to fish heaven. By this I mean that if the shipment comes in on a Thursday, wait until Monday or Tuesday to buy the fish. The lot will have "settled" some, with a percentage of the very weak fish dying off over the weekend. Yes, you run the risk of someone buying a few over the weekend but you'll have the hardy ones on Monday.

• Keep a school! Tetras like to hang together fairly tightly, swimming together in unison. Denying this instinctive behavior to Cardinal Tetras is a sure way to stress these fish to death. Some folks say a group of six of these fishes are enough.  I say yes, but only if your tank is a ten gallon size! Larger tanks really give the fish the ability to school, and they will do so much better if you try to emulate nature. Hence, in a 150 gallon, you can have 150 or so of these beauties, in a 90 gallon tank, 75 or so is a good number.  The best way to purchase such quantities is to let the pet shop know you want a large grouping (now you know why I like to develop trust with my local fish stores). Most of the time I purchase my fish in quantities of about 30 or so.  I will go into the store, see the tank of Cardinals, and if the owner says they are doing well, I buy the entire lot. Within the next couple of weeks I repeat the process. I quarantine each new lot of Cardinals  for about a week to be sure they don't have any diseases and then move them into the show tank. Adding fish to a tank is always putting existing fish at risk, so I would rather buy a big lot once or twice than to purchase 10 - 12 fish five or six times. It's just too risky -- even with quarantining. 

• Watch how the fish are being netted from the pet store's tank. Sometimes, you'll get a new employee or someone who doesn't know too much about Cardinals, and they will not easily catch the fish.  Cardinals are VERY reactive to stress ... in a BAD way. Over stressing the fish when they are being netted is the number one reason why some fish die in the bag before you even get them home.

• Acclimate the fish slowly. There are all kinds of ideas out there about the best way to do this. Floating them in the bag for 10 minutes and then releasing them is NOT recommended for these fish. I used the drip method of acclimation (placing the fish and bag water into a bucket and dripping tank water into the bucket over several hours). Over the last year or so, I've modified the process and add water at the rate of about a quarter of a cup every 15 minutes. I've had similar good success and it is very rare that I lose a Cardinal once they have reached my home.

Well, that's the process I use in selecting, purchasing, quarantining and acclimating my Cardinals.  Next time, I'll share not only how I keep them alive, but how to get them to grow close to two inches long!