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Keeping Juvenile Serrasalmus piranha -
By Evan Thompson
Over the years, time and time again I've seen the same questions asked by
hobbyists getting started with young Serrasalmus fishes. What it
boils down to is "Why is it the way it is?"
Nine out of ten times these fish are imports being caught in a natural
environment, held and shipped to the states (or other country), then held by
the dealer before they're purchased and taken home or quite possibly purchased
and shipped again to a hobbyist from a far away location. What happens
frequently with new piranha hobbyists is a kind of profiling
that stems from many different origins...possibly from other inexperienced
piranha keepers, salesmen or even Youtube videos that highlight how aggressive
these fish are. This profiling leads to a false understanding of what
they are getting, which in turn leads to impatience, then frustration and then
finally a lot of times giving up on the young Serrasalmus
which can and
many times does, go down bad roads...
I am in no way an expert
on these awesome predators.
What I am is a hobbyist that got started with these fish many years ago, and
learned through experience what to expect, what is fact and what is
fiction. My only reason for this write-up is to hopeful clarify these
animal's true behavior so that the new hobbyist has a better understanding of
what he/she is getting into, hopefully BEFORE they purchase the animal,
and is able to decide if this fish is right for them.
Are these fish aggressive? YES
Are these fish territorial? YES
Do they show this behavior immediately? Not likely.
What one has to understand is that, especially when juveniles, Serrasalmus
can be EXTREMELY skittish, sometimes to a point where it begins to feel to the
hobbyist as if he/she is keeping an empty aquarium. This
skittishness can last a very long time. Personally, the longest I've ever
dealt with an extremely skittish Serrasalmus
was over a year,
however, I have read accounts of this skittishness lasting more
than two years, so its easy to see that if the new hobbyist is not
expecting this, it can and will become frustrating. This behavior is
absolutely normal and I cannot stress enough that it should be EXPECTED of
the juvenile Serrasalmus
to act in this way. The reason for
this behavior, summed up, is survival. When these fish are young, they're
what are called ambush predators,
meaning they spend their day hiding
amongst aquatic foliage, driftwood, submerged root systems, rocks and other
hiding places, waiting for a quick and easy meal to come within grabbing
range. At the same time, they're constantly trying to avoid becoming a
meal themselves to larger predators. This is what they are wired to do
in the wild, so when they're introduced to an aquarium environment, their
natural instincts are what they go by and, coming from the fish's perspective,
the hobbyist leaning in close to the front panel of the tank looks like a huge
Not every individual Serrasalmus
displays this behavior. There are
some that become outgoing quickly, but in my experience, the vast majority need
time to come around. Some take longer then others...some take weeks and
others take years, but the best thing the hobbyist can do is provide a good
quality of life and be patient.
Many experienced and novice hobbyists alike have tried many different routes to
fast track their Serrasalmus to show more personality. These
- Keeping the fish in a bare tank, thus forcing him into the
open. The idea is that over a short period of time, the Serrasalmus
will realize that the hobbyist poses no danger to him, and he will quickly come
out of his shell.
- Packing the tank with many hiding places, and allowing the
fish to hide as much as needed...allowing it to grow out of this ambush
predator mentality naturally over whatever period of time it takes. I
personally have always used this tactic and I've found that although it may
take the Serrasalmus longer to come around, depending on the individual
fish, this way is far less of a shock to the animal.
- Some people introduce dither fish (*typically small,
fast, schooling fish that act as targets for the primary fish to interact with.
Causing them to come out into the open more frequently). Personally, I
feel that this is counterproductive if you're looking to get your Serrasalmus
out of hiding, due to the fact that it triggers the hunting instinct, making
the Serrasalmus try to become invisible as he waits for the perfect
The new hobbyist will most likely see many keepers of adult Serrasalmus
rhombeus being housed with small schooling fish without issue.
Keepers of juvenile Serrasalmus, even those specimens that spend day after
day hiding, should understand that their fish are extremely fast and
extremely aggressive to other fish, particularly those small enough to create a
prey drive. It goes without saying though, that equally bad things can
happen to fish that matching the Serrasalmus size. Many
people have had horrible experiences when attempting to house two
Serrasalmus in one tank with a tank divider in place, keeping them
separate; Tragedy occurs when the divider is knocked down and their
territorial drive kicks in.
In short, I do not recommend tankmates for juvenile Serrasalmus and
if one chooses to go forth and try, casualties should be expected.
Some of the practices that the new keeper can rely on to aid him are are
also some of the most basic:
1) - Keep your juvenile Serrasalmus tank in a high
traffic area of your home. Get him accustomed to seeing people all day
everyday. My favorite spot that I've placed a tank is where it's at right
now...directly behind and butted right up against my couch. The design of
my living room, thankfully, permits me to do so, and I've been very pleased
with the outcome.
2) - Place tank lighting on a timer. The rhythm
of lights on, lights off at the same times daily best simulates a
day/night cycle. (With very newly introduced Serra into the aquarium, my
personal practice is to leave the lights completely off for the first 3 days or
so that I have him home while he acclimates to his surroundings.)
3) - Purchase a good quality heater that keeps the the tank
water at a steady temperature. Avoid temperature swings.
4) - Keep clean, healthy water through good filtration and
weekly/bi-weekly water changes.
5) - A healthy varied diet of prepared foods. There have
been plenty of great, informative articles and threads written on this subject
so I'll not be diving in much here, but what I will say is that it is
common for these fish to only accept live foods in the beginning,
often being quite stubborn about what the keeper is offering.
The reason for this is that while these fish are being held by the dealer, most
feed live feeder fish of some sort for the ease of getting the piranha to
accept the food offered. It is not uncommon for the Serrasalmus
not to accept anything other then live once it's brought home. There is
no need for the keeper to worry if the Serrasalmus just will not take
the chunks of frozen tilapia....offer the food and remove it, if uneaten, after
an hour or so to prevent contaminating the tank water. The Serrasalmus
will not starve himself....do this every few days and eventually (might take a
week or two) it will take the food. It is quite impressive how long even
a 4 inch Serrasalmus can go without eating even a morsel of food so a
few weeks will not hurt it. (Similar to the lighting topic, with very
newly introduced piranha, I withhold from feeding for a week or so while the
All of these steps can be taken to help ease the newly imported Serrasalmus
into life in an aquarium, but the fact of the matter is that nothing is going
to change the behavior of an aquarium fish overnight. As previously
stated, quality of life, time and patience are the keys to successfully raising
these fish from juveniles. With many, many individual Serrasalmus,
there are no shortcuts. As I've stated before in many other threads, I
have never kept a single Serrasalmus that was not curious about what was
going on in his tank and in the environment surrounding his tank. Did
they start out that way? Absolutely not! Some were more difficult
than others, but with all of them, I initially dealt with long periods of
(sometimes extreme) shyness until a bolder personality developed.
Another topic that I've often seen is an aquarist asking how he
can train his Black (Serrasalmus rhombeus) Piranha to be more
aggressive, like videos seen online. This is actually quite a
comical question to me--persons asking this question should come to terms with
the reality that their Serrasalmus is a fish, not a German
Shepard. These fish are aggressive, especially as they mature in an
environment their comfortable in, but if having an extremely aggressive
predatory fish is all the aquarist is looking for he/she is better suited
looking outside of keeping Serrasalmus piranha. I and many others
understand the attraction to having an aggressive fish that chases everything
relentlessly, however the amount of time needed to develop that boldness in a
young Serrasalmus is often much longer then a casual hobbyist is willing
to commit. Then there's always the possibility that the extreme
aggressiveness might never develop as well.
As they grow, and the fish become larger and more robust, they will begin
to develop a deeper aggressiveness toward threats approaching
their territory, simultaneously showing more of a curiosity of their
surroundings. I wouldn't go so far as to claim that these fish
develop an attitude of wanting to chase and bite, but they're much
quicker to confront and stand their ground. At this point, it is not
uncommon to begin seeing the fish pacing the front panel of the
aquarium, the whole time making contact between the glass and his
lower jaw. This can cause a callus to develop, appearing as a bump on
the end of the jaw that is commonly referred to in the hobby as a chimple.
In most situations, they're small and pose no real threat although they can be a
slight eye sore to the keeper. In minor cases, they can show up and
heal on their own without scarring. In the rare occurrence that they
become serious, the keeper should look into a larger sized aquarium, and in the
meantime, focus on keeping the water quality as high as possible to prevent
The new keeper should take into account that these fish can grow to large sizes,
depending on the species. There are basically two species_Serrasalmus
rhombeus and Serrasalmus manueli (*Manny)_ that have the ability to
grow past 15" in the wild. Most of the other many species of Serrasalmus
will not surpass 10 inches. All that being said, Serrasalmus rhombeus
are very popular fish to purchase, especially when young, and the new keeper
should be informed that when raised in captivity, S. rhombeus have
not reached the lengths that they can obtain in the wild. 10 inch - 12
inch is a reasonable length to expect and even those lengths should
be anticipated to take a very long time to achieve due to these fishes
notoriously slow captive growth rate. It does not mean that it is not
possible to grow them out to 16 inches+ given the correct water and food
stimulants. I personally, have just never seen it done and
proven. I have zero experience with Manny's, but I'll say that slow growth
will most likely mirror that of S. rhombeus, and it may be even
more pronounced because they tend to be more sensitive to water quality issues.
Without getting into too much detail about tank sizes....A standard 55 gallon
aquarium is a very popular tank size that will do well for most Serrasalmus_
bigger is always better of course, but for many of the species this tank will
work. However, the common 55 gallon should not be used to house Rhom's and
Manny's for the long run. They can be used and are a great tank for grow
out purposes, as long as the keeper understands that this would be
temporary housing until a 48" x 18" or better yet a 48" x
24" tank will be needed.
They will not outgrow that 55 gallon quickly. A young S. rhombeus
will typically make it to 5" - 6" mark at about a year, then their
growth slows down considerably to about an inch per year give or take.
Once they get to about the 9" mark, growth lengthwise slows down even more
so. If the new keeper currently has a 55 gallon and wishes to get a
juvenile S. rhombeus (lets say a 3" specimen) he/she should expect
to upgrade at about 2 - 3 years.
I could go on and on about many different topics here, but my goal was
to merely break the ice for new and future keepers of these great aquarium
predators. I recommend that the aquarist look into further writings
of all kinds related to keeping these fish as the more information you have, the
more comfortable you will be making needed adjustments and addressing any
problems/questions you may experience. Keeping Serrasalmus piranha has,
for me, been a very rewarding experience and if I was able to help just one
novice piranha keeper understand juvenile Serrasalmus a bit more with
this write up, all of this typing will have been worth it.
Thank you and always remember, when it seems that this Serra that you purchased
6 months ago is always hiding and is never going to stop, it will. Hang in there
because its all the more rewarding when it finally does.
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