Red Tetra behavior

Question
Hi Nicole,
We have four red tetras.  At least, that's what we call them.  I am not sure of their official name.  Their main color is red and they have a black feathery dorsal fin with remaining fins and tail an orangish red.  If you happen to recognize this fish, maybe you can explain some odd behavior we've observed recently in two of them.  Two of them have turned dark on the top halves of their bodies, like a dusky blackish red.  They swim after the two smaller red tetras vibrating and shaking.  By evening, their color reverts to normal and the behavior stops.  We suspect it is a mating behavior.  Have you ever seen this before?

Thanks,
Sybille


Answer
Good evening Sybille, thank you for your question.

Two possibilities for your tetras, as I see it. You may have Hyphessobrycon sweglesi, the Red Phantom Tetra:
http://www.fishinthe.net/html/fishguide/fishguide_fish.php?FC=173&nl=&nt=1

Or you may have Serpae Tetras, Hyphessobrycon callistus:
http://www.fishinthe.net/html/fishguide/fishguide_fish.php?FC=129&nl=&nt=1

I am leaning towards Serpae Tetras. Their care is similar, in any case, and you can read all about it at this site, or Google the common names of both species. There are several scientific names that refer to both these, respectively...

I agree with you that this is spawning behavior. Serpae tetras are known to be nippy, but I have found that in a small school, they tend to be close knit and their aggression is curbed - except perhaps at spawning time! There must be something that happens during the day to stimulate them. Perhaps that's when you feed them especially delectable foods? Maybe they get the noonday sun shining into their tank? Performed any large water changes recently? It could be nothing more than your good husbandry, in fact.

I would not be concerned. There is lots on the web in regards to spawning these species, whichever you may have. Unless you are interested in rearing the fry (since you likely have a mated pair) I would let them scatter their eggs freely. They will probably be consumed. Even if they are fertilized and the fry are born, without lots of cover (such as plentiful hornwort, cabomba, or other fine leaved plants) the fry will be eaten, if not by the tankmates then by the parents themselves! Most everyday fish have a lack of parenting skills, with the notable exception of cichlids...

I hope that answers your question. A word of caution: spawning can sometimes become a bit violent. I wouldn't worry, but if you feel there is bullying going on I would try suspending the aggressor in a roomy net at the top of the water column for a few minutes, or installing a tank divider. They are available at many local fish stores, or you can use egg crate cut to fit. Egg crate is available in the lighting panel section of a chain hardware store.

Take care!
Nicole