FAQs on Otocinclus
Related Articles: Otocinclus, Loricariids,
Related Catfish FAQs: Otocinclus 1, Otocinclus 2, & FAQs on: Otocinclus Identification, Otocinclus Compatibility, Otocinclus Selection, Otocinclus Systems, Otocinclus Feeding, Otocinclus Health, Otocinclus Reproduction, &
Catfishes of South and Central America, Loricariid Identification, Loricariid Behavior, Loricariid Compatibility, Loricariid Selection, Loricariid Systems, Loricariid Feeding, Loricariid Reproduction, Loricariid Disease, Catfish: Identification, Behavior, Compatibility, Selection, Systems, Feeding, Disease, Reproduction, Algae
Otocinclus staying at water surface
I purchased 5 Otocinclus 4 days ago and have them in a 10 gallon
quarantine tank. If all goes well, I plan to add them to my 55 gallon
show tank after a month or so to help control the brown diatom algae (I
think I must have silicates in my tap water causing the brown algae
growth because it has always been a problem in this tank for over a
<I wouldn't get my hopes up on this! Five Otocinclus won't have a
massive impact on a 55 gallon tank, and while they eat some diatoms,
they prefer green algae. Snails, particularly Nerites, are the best at
eating diatoms, but more often than not, if you get the rest of the tank
balanced, and plant growth strong, a simple wipe of the front glass is
enough to keep the diatoms minimised.>
Today one of the Otos started hanging out at the very top of the tank on
the glass right at the water surface. Sometimes I think its nose might
even be just out of the water. Is this something I should be worried
Could this be a sign of low oxygen in the tank, and if so what should I
<Yes, can easily be this, but also other problems. Otocinclus tend to be
starved on import, and their survival rate isn't good. Getting
them through the first month is a good sign. I often recommend getting
something like twice as many as you need, because that really is the
level of mortality we're looking at. Some retailers do get them in
healthy condition prior to purchase, in which case you may do a lot
better than this. Also some species, like Parotocinclus jumbo, seem to
be a lot tougher. But the average Otocinclus from the average pet store
aren't a safe investment.>
I set up the quarantine tank about 5 days before purchasing the new
Otocinclus. I filled it halfway with water from my larger tank and then
the rest of the way with Prime treated tap water, and moved a filter
cartridge from my larger established tank to the quarantine tank's hang
on back filter. The larger tank is fully cycled and has been stocked
with the same fish without any problems for over a year. The quarantine
tank is decorated with fake plants and has small rocks on the bottom. I
also moved some of the rocks from my larger tank that were covered with
brown diatom algae so the Otos would have something to graze on when I
The new Otocinclus seem to really love the brown algae.
<Quite so. They're aufwuchs grazers and consume both diatoms and green
algae, but also various micro-invertebrates. A good green turf would be
I have also been feeding them small pieces of Hikari algae wafers and
today I added a small piece of blanched zucchini.
I remove any uneaten food daily. I checked the water conditions today
and they were Ammonia 0, Nitrite 0, Nitrate <20, GH 75, KH 300+, pH 7.5.
Any ideas why this one Oto is hanging out at the water surface?
<Hard to say. Stress, sickness, sensitivity to something... by all means
observe and optimise water conditions. But no treatment as such beyond
hoping for the best.>
Thanks so much,
<Most welcome. Neale.>
Question about my Oto cat
A while ago I had a 10 gallon tank with 4 Guppies and an Oto
<A bit small for Guppies.>
The Oto did just fine, was always eating, and very lazy.
<Shouldn't be "lazy" at all. This SCHOOLING
species should be buzzing about in a group of five or more
specimens, pretty much all the time, flitting from leaf to
Now I have a new tank with 4 GloFish and an Oto Cat.
<Again with "an" Otocinclus. They're schooling
fish that don't do well singly.>
This is my second Oto for this tank the first died after two
<Unfortunately a very common experience. Most aquarists kill
their specimens quite quickly, and retailers aren't any
better at all.>
When I took it back the pet store they said it was because it was
<Likely correct. Otocinclus are notoriously difficult to feed.
In the wild they consume green algae (not diatoms, and not hair,
bush or thread algae either) alongside what is called aufwuchs,
tiny invertebrates that live among green algae. In captivity they
can be maintained in mature tanks with a combination of green
algae, finely minced seafood, and standard algae wafers, but they
don't compete well for food and shouldn't be kept
alongside greedy fish that feed in the same way, e.g., loaches or
So I got another one and put blanched zucchini in the tank, as
many sites said they'll like.
<Some specimens will eat softened vegetables, but it's not
Problem is he hasn't touched it. I don't want to starve
another one.. I have also put in an algae wafer and he hasn't
touch that either. He keeps sucking the sides and swimming all
over from side to side of the tank like he's looking for
something to eat. Any suggestions??
<Will likely not settle down without four or more friends of
his own kind.
In a group this species is happier, and therefore more ready to
Should I just wait to see if he makes it or not?
<If you want, but I'd put money on a swift death.>
Also right now I'm leaving the light on 12 hours to try and
<Green algae needs strong lighting to grow. If you have plants
that grow so quickly you have to remove a handful of foliage
every week or two, you probably have the right amount of light.
If your plants basically sit there and throw out the odd leaf
every few weeks, then you probably don't have strong lighting
and the dominant algae types will be diatoms (the brown scum on
the glass) and red algae (hair, brush and thread algae, which
aren't red, despite the common name for this group).>
I'm stumped I don't know what else to do.
<I'm surprised you're stumped, because the aquarium
literature on Otocinclus spp. is actually quite good. Most any
tropical fish book will tell you that these catfish need to be
kept in groups, need cool water (22-25 C/72-77 F), and are
difficult to feed.>
I attached 2 picture to see if your think he's okay or not.
He's slightly blurry because he wouldn't sit still.
He's very active. Thank you!!
<Glad to help.>
P.S The pet store got new fish in Thursday and Friday when I
brought my dead one back and got the new one, he was the last one
left. I'm not sure if they just sold that quick or if there
was a reason to why they didn't get more.
<Many pet shops buy Otocinclus because they know [a] they die
quickly and [b] people will keep buying new ones to replace any
losses. Somehow, there's a rumour that Otocinclus are good
algae eaters for small tanks.
That's total and 100% rubbish, but sadly you'll hear it
said in some pet shops and written on web sites by people who
perhaps don't know any better.
There are some excellent catfish sites, like PlanetCatfish, that
will provide very useful information.>
It just seemed weird to me.
<Not weird; typical.>
I checked and there was no dead fish in the tank so I assume they
were all in good health. I was thinking of getting another one so
he has company, but no other pet stores around here sell them. If
this one doesn't work out I'm going to stay away from
them for a while as much as I don't want to... I really like
these little guys.
<I agree with you that this genus is best avoided by casual
aquarists. They can work in largish (20+ gallons?) systems with
bright lighting and lots of plants, where there's enough
growth of green algae to supplement algae wafers and other such
foods. In smaller tanks and less brightly lit tanks they become
totally dependent upon the aquarist to feed them, and that is
very difficult to do. Not impossible, but difficult, and you do
need to ensure two or more small meals per day. Kept singly the
poor thing may well be so nervous it'll never feed adequately
well. For small tanks Nerite snails are infinitely better
algae-eaters, not least of all because they consume diatoms. Hope
this helps. Cheers, Neale.>
|Re: Question about my Oto cat
Thanks for your help Neale.
So basically I need to get more, which is impossible because the
pet store is out,
<Otocinclus spp. aren't rare, and shopping around or online
should yield results. Alternatively, ask your retailer to order
or take him back/wait for him to die and get something else..
do you have any other suggestions other then snails? I always start
out with one snail and end up with like 10.
<Nerites don't breed in freshwater; they lay eggs, but the
larvae need to drift to the sea and develop in the plankton. This
is why I specifically recommend Nerites. One or two per 5 gallons
is about right.>
At pet smart they have albino Cory catfish in the tank with the
Glofish but it says they get to 3" and I think that's to
big for a ten gallon though it says 10+ gallons on the tag.
<Albino Catfish are typically Corydoras paleatus, and while they
could be kept in a 10 gallon tank, they wouldn't be my
recommendation. Yes, exceptional specimens can exceed 7.5 cm/3
inches, though 5 cm/2 inches is much more typical. Do read the
following for more on stocking:
Would it be okay if I moved my Oto out of the tank to feed or would
it stress him out more.
<Yes, that would be stressful. Guppies shouldn't compete
against him for food, but Corydoras surely would, at least in a
tank this small. Nerites and Cherry Shrimps would be the most
logical bottom feeders.>
I'm really wanting to keep him around. Thanks again.
Otocinclus.. sys., comp.,
My name is Jessica, thank you for your help in advance. I have been
keeping Goldfish ever since I got my first ten gallon aquarium at the
age of nine.
For the past two years, I have had a 29 gallon freshwater planted tank,
which is also home to one brand new, week old, two inch Fantail
Goldfish and two Otocinclus.
<Mmm... not really compatible fishes... like very different water
The tank parameters are as follows, pH 6.4,
<Low for Goldfish>
Nitrites 0, Nitrates 20ppm or less,
<I would not let the NO3 concentration get any higher than this
Ammonia 0, and temp 70-72F. I do a weekly 25-50% water change and
vacuum the gravel at the same time while tending the plants. It is well
water so I don't need to add a dechlorinator. I bought the two
Otocinclus about two months ago and they have done an amazing job
cleaning up the algae in the tank. At the time the aquarium was home to
an eight inch, five year old Bubble Eye Goldfish who has since passed
on. His one eye bubble got so big that he kept catching it in his
mouth. It became irritated and in the 24 hours that I was not there it
managed to become infected and swollen. I placed him in the hospital
tank and gave him antibiotics but sadly his eye popped and he died two
days later. Since then I have been substituting the Otocinclus's
algae diet with some zucchini and Spirulina wafers and have left the
back and sides of the tank alone for them to clean. When I first got
them they both had Ich and one of them had almost its entire caudal fin
missing. Unfortunately, I read that this was rather commonplace during
the shipping process.
<This is so>
Anyway, its fin has regrown and they both seem to be doing fine. What
concerns me is that their dorsal fins always seems to be held tight
against their bodies, they have been this way since I got them, is this
just normal behavior for them?
<Mmm, yes. A general statement re freshwater fishes is that their
fins are "down" for most of the time, vs. marine fishes,
whose fins are "up" most of the time>
They seem happy otherwise zooming around the tank and they really love
their zucchini, although the new goldfish is fighting them for it.
Also, I was thinking of raising the pH just a little bit, up to 6.8,
and to this end was thinking of boiling some shells, cracking them, and
placing them in a glass bottle in the tank.
That way the fish could not get cut on them and they would be easy to
take out if the pH got too high. Do you think this is a good idea or
would you recommend to just leave the pH alone as is?
<I might instead add a bit of sodium bicarbonate (baking soda) to a
given batch of make-up water (in storage and tested ahead of use) to
get a proportion of how much you'd be adding to raise the pH on a
regular basis... but the shells are again a good/safe source. Bob
Cory/Oto behavior change
Thanks as always for all that you do.
<Kind of you to say so.>
My question concerns a change in behavior by some of the fish in my
tank. Tank specs as follows:
Tank: 10 gallon standard
Filtration: Aqueon 10 HOB with pre-filter sponge (x2) each rated for
Above tested via API Freshwater Test Kit
Total Alkalinity: 180ppm (tested via strip... not really sure what this
<Middling hardness, fine for most purposes.>
Total Hardness: 120ppm (tested via strip... not really sure what this
<Similar. Do read:
20% water change weekly
Flora (moderately planted):
Cryptocoryne wendtii x2
Cryptocoryne parva x2
Anubias barteri v. 'Nana'
Ceratopteris thalictroides - rooted
Remnants of Java moss - mostly removed as it was constantly infested
with thread algae
<Yes, never had much luck with this plant myself. Always seems to do
well where I don't want it, but badly everywhere else.>
<The world's best ammonia remover! A blessing of sorts, but a
nuisance I know.>
Corydoras pygmaeus x6
Boraras maculatus x15
Otocinclus affinis x3
Assassin Snails (started with 2 adults, now numerous juveniles)
Hitchhiker pond snails
<Sounds grand! It's a real joy to read about a sensibly stocked
10 gallon tank.>
Tank was set up and planted in October, stocked in January.
I've observed a change in behavior in my Corys and Otos over the
last few weeks. In the past, the Otos would spend time on the front and
side glass of the tank during all hours of the day/night. Lately, they
stay in the small space between the HOB filter and the back glass of
<Possibly more food there?>
They will venture down to the substrate at night to eat algae wafers
(Hikari brand), but ignore the blanched zucchini and carrots I place in
the tank which they used to eat with gusto.
The Corys, while always skittish, used to venture around the tank in a
shoal, especially when I fed the Rasboras. After not seeing any of them
for weeks, and assuming they had perished somehow, I found them hiding
in a tiny crevice, all on top of each other, between the driftwood and
the substrate, when I shined a flashlight into the tank to try to find
them. They also now seem to venture out only at night for the sinking
wafers (Hikari brand) I place in the tank at lights out. I know that
Corys are nocturnal in the wild, but this is a recent development,
hence my concern.
I'm not sure what caused the change in behavior as my feeding and
maintenance regimens have remained the same. Water quality has also
<That would be my first though, as well as variation in pH and
problems with oxygenation. Since both Otocinclus and Corydoras prefer
cooler rather than warmer conditions, check the temperature. 25 C/77 F
is the absolute tops for both species.>
My first thought is an aggression issue with the Rasboras, but I have
never observed any aggression.
I had also thought that I might need to add Corys to the tank to see if
increasing the size of the shoal would bring them out into the open
more often, but I believe my tank to be fully stocked as is.
<Oh, I'd chance it. With all the plants I think you'd be
fine. I'd keep at least 5 Otocinclus, and maybe double the number
of Corydoras pygmaeus. All these fish are so small that their impact on
water quality would be fairly trivial.>
Do you have any thoughts on what would cause this change in behavior
and if there is something else I should be doing?
<My guess would be something is scaring them -- too much overhead
light, noise/vibration outside the aquarium, banging doors or some
such. Direct sunlight can also be a thing. I have a 15 gallon tank that
gets direct sunlight for a couple of months of the year, and the way
the fish behave becomes noticeably different during those times. The
Corydoras paleatus in particular cluster in one particular shady spot
under the Anubias mother plant.>
Thanks in advance.
Otos coloration: Sick or normal?
I got four new Otos on Monday. Stupidly, I put them in my tank without
first a quarantine (this won't happen again, trust me). I may just
be paranoid but I am wondering about their coloration. It looks
splotchy to me and I was wondering if this is normal or if it might be
something I need to take care of. < Hard to say what the
problem is. It is normal for fish to have a fright pattern when being
introduced into a new tank. As they begin to feel more comfortable than
they start looking more normal. Many times these algae eaters are
starved at the wholesalers and at the local store. I would place an
algae wafer in the tank at night to make sure they are getting
something to eat. If the splotchy pattern continues with all the fish
or gets worse then I might start thinking there is a problem.
-Chuck> I am attaching two pictures. If you need any other
details, please ask. Thank you for your time. David
Once playful Otos are now
lethargic 7/28/06 Hello there, <Hi from... HI!>
For the past 5 months, I have owned a 46 gallon, unplanted tank,
containing 10 rummy nosed tetras, 10 black phantom tetras, 4 peppered
Corys, and 3 Otos. <Better with live plants...> The Otos were
originally quite playful, moved around the tank, stayed within view,
interacted with other fish and ate any algae that
appeared. However, for about the past month, the Otos have
been in hiding. <Something in the way of water quality changed>
Now I hardly ever see them, and algae is building up on the glass and
plastic plants. They don't appear to be sick, and
none have died. All the other fish appear to be
normal. My water temperature has increased to about 82
degrees due to the warmer summer weather, but besides that, I can't
think of anything that I've changed. I do 20% water changes once
every week or two, and nitrate level is 12.5 mg/L or lower (my test kit
measures only measures 1, 0, 12.5, and 25 mg/L). I don't
add any "Oto specific" food to the tank. Might I
simply have more algae than they can handle, allowing them to become
more "lazy"? Do you have any thoughts on the
matter? <Yes... I definitely would add some live plant material
here... Will address many possible ills, shortfalls that could be at
play here... Dissolved oxygen, food, shelter...> Thanks in advance
for your help. Bonnie <Welcome. Please read here: http://wetwebmedia.com/FWSubWebIndex/otocinclusart.htm
and the linked files above. Bob Fenner>
Oto loses colour Hi, We have a sick Oto which has suddenly
lost its pigmentation and is looking a sickly grey. It is swims
weakly, sometimes floating at the surface and drifting in the
current. Otherwise its body, fins, etc. look in good condition.
Can you suggest any remedy or is this something to do with the
tank conditions? We have a 180-litre (40 gallon) community tank
with 9 guppies, 3 minnows, a Pleco and 5 Otos altogether. It has
some live and plastic plants, a couple of logs and a small rock
pile (slate), i.e. there is a relatively large surface area
available for the Otos to graze on. It has been set up for about
3 months, but, about 3 weeks ago, we had problems with water
quality, fungus and white spot. These were successfully treated
with 10% water changes every day and ESHA 2000 and EXIT.
Treatment finished 7 days ago. Current conditions pH = 7.8, KH =
6Â°, GH = 12Â°. Ammonia, nitrite and nitrate
levels all low. We have isolated the sick Oto. Grateful for your
advice. Regards, Quentin <Hello Quentin. Let me start by
making a general statement about Otocinclus: they are extremely
difficult to maintain, and the vast majority die soon after
import. The problem is that they feed on really only a single
thing -- aufwuchs, a combination of green (and exclusively
green!) algae together with the tiny invertebrates that live
within that green algae 'biofilm'. Unless you have an
established aquarium of large size with very strong lighting (2+
watts per gallon) so that green algae can flourish, it is
exceedingly unlikely your Otocinclus will be getting enough to
eat. How many months it is before they die is variable, but
starve they will unless ample substitutes are provided. Algae
wafers can work, but Otocinclus find it difficult to compete with
other fish, and the fact you have other algae-eaters,
specifically guppies and Plecs, makes this point critical. For
this reason, I simply don't recommend them as community fish.
Furthermore, while water chemistry itself isn't all that
important, temperature and water quality are very important. Most
people keep their tanks far too warm for Otocinclus, which come
from cool, fast-flowing streams and want something in the 20-25
degrees C range rather than the usual 24-28 degrees C most people
maintain standard community tropicals at. In other words, a
near-subtropical, fast-water tank with things like White Cloud
Mountain Minnows and Danios is much closer to what they want than
a standard Amazon community aquarium. You also mention ammonia
and nitrite levels as being "low" -- but be under no
illusions here, Otocinclus MUST have zero levels of both. If you
can detect either in your tank, it is simply not suitable for
Otocinclus. In all likelihood the sickly specimen will be dead
within a few days, so treatment here is irrelevant. Optimizing
water quality, lowering water temperature, providing ample green
algae and suitable invertebrates would all be things you could do
to help the isolated fish, but that's about it. For the rest,
you need to ensure your aquarium satisfies the demands outlined
above. Hope this helps, Neale.>
Re: Oto loses colour 7/6/08 Neale, Many thanks for your
helpful advice. The Oto has now died, sadly. However, we will
develop the tank environment to make it better suited to
Otocinclus. They are an entertaining fish to watch. <Yes they
are. In the right tank, they can be great fun. In the wrong tank
though... My most recent run-in with this species was a disaster,
some of the Otocinclus deciding to graze on the mucous of some
large benthic gobies. They have a reputation for attacking big,
slow moving fish such as Discus and Angelfish. On the other hand,
aquarists like Takashi Amano make much use of Otocinclus in
planted aquaria, usually alongside Caridina shrimps as a superb
combination for green algae control in brightly lit aquaria.>
Thanks again. Your website is a mine of information and a great
support to the budding enthusiasts in our family. Regards,
Quentin <We're happy to help, and thanks for the kind
words. Cheers, Neale.>