FAQs on Otocinclus Systems
Related Articles: Otocinclus, Loricariids,
Related Catfish FAQs: Otocinclus 1, Otocinclus 2, & FAQs on: Otocinclus Identification, Otocinclus Behavior, Otocinclus Compatibility, Otocinclus Selection, Otocinclus Feeding, Otocinclus Health, Otocinclus Reproduction,
Loricariid Genera: FAQs on: Ancistrus, Baryancistrus, Genera Farlowella, Loricaria, Sturisoma,
Rhineloricaria: Twig Plecostomus, Genera Glyptoperichthys, Liposarcus, Pterygoplichthys, Sailfin Giants
among the Loricariids, The Zebra
Pleco, Hypancistrus zebra, Hypostomus, Peckoltia: Clown
Pseudacanthicus, Scobanancistrus, L-number catfish,
& Suckermouth Catfishes of South and Central
Selection, Loricariid Systems,
Loricariid Feeding, Loricariid Reproduction, Loricariid Disease, Catfish: Identification, Behavior, Compatibility, Selection, Systems, Feeding, Disease, Reproduction, Algae
Soft/er, acidic water... highly oxygenated;
systems... with green algae (not filamentous) present
Flow rate for a stream manifold Otocinclus vittatus tank
Thanks for putting together a very informative site.
I'm interested in trying to breed the Otocinclus vittatus species, and was
wondering what you might suggest as a flow rate for a stream manifold type tank
<Mmm; depending on the arrangement of the motive force... several turn overs per
I've been attempting to research the rivers these naturally occur in, but can't
really get a feel for the flow rates. I'm all for the guess and test method as
an option, but thought you may have some material on hand.
<Have been to where some members of the genus are collected... flow rates are
seasonally high/brisk to quite calm>
I've been keeping about 15 in a school in a 20 gallon with a small school of
cardinal tetras, and noticed that the Otos are most active around the output for
an Aquaclear 50 or after water changes.
As such, I'm thinking they might appreciate a bit of current or higher dissolved
<Ah yes; concur>
As such, I was thinking of installing a manifold into a new tank similar to what
folks use to keep Hillstream loaches, though at considerably lower flow rates.
Current tank is a Walstad-type setup, extremely heavily planted with a
gravel/sand cap over soil. Would transition them to a new tank after
establishing it for a while.
<I do consider that this is a good idea... again, ten or more turns/h...>
<Thank you for sharing. Bob Fenner>
Re: Flow rate for a stream manifold Otocinclus vittatus tank
<Thank you for sharing. Bob Fenner>
Much obliged! That will be very helpful. I'll start out around 10 turnovers an
hour and go from there.
<A delight; and please do keep us abreast of your observations, experiences
Re: Flow rate for a stream manifold Otocinclus vittatus tank
<A delight; and please do keep us abreast of your observations, experiences
Happy to, thanks!
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
Oto question, sys., comp.,
Here's a little background.
My wife and I recently setup a new 10 gallon tank.
<A small tank; not recommended for community tanks.
We got an internal filter. We use a heater (which raises the temp by 4
degrees), the temp is usually 73*F without the heater, but based on the
fish we had, I thought 77*F would be a better temperature,
<Does depend on the fish.>
and our heater doesn't have a setting (other than on or off). For
now we leave it plugged in and achieve 77*F. We started with 2 Neon
Tetras, 3 Black Mollies, and 1 Otocinclus.
<72-75 is ideal for Neons and Otocinclus, but tank-bred, fancy
Mollies really need slightly warmer conditions, 77-82 F.>
One of the Neons died within 24 hours. The other neon became so lonely,
it stopped playing in the bubbles, it stopped eating, and died of
loneliness within a week (even the mollies wouldn't play with it
when it tried).
<Let's step away from ideas of "playing" and
"loneliness". Neon Tetras are difficult to keep unless you
have cool, soft water. You're aiming for pH 6-7.5, 3-10 degrees dH.
They won't do well in the hard water Mollies MUST have to stay
alive. So these two species are NOT compatible. Neons also need to be
kept in groups of 6 or more.>
We added 2 more Black Mollies, all these fish so far have come from
<Mollies really won't do well in 10 gallons of water. The males
are aggressive towards each other and the females. They are also very
sensitive to poor water quality, making them bad choices for new tanks.
Do read here:
After a few more visits to PetSmart, we noticed that some of their fish
had Ick. We then noticed ours did too. We tried 2 treatments (1 and
then another 24 hours later as per the directions) of a bubbling type
tablet that was supposed to clear the Ick.
<Hmm'¦ with Mollies, your best bet is the salt/heat
It removed smaller spots of the Ick, but the Mollies still had large
amounts on them. Unfortunately we couldn't afford the treatment
when we first noticed it.
<Salt is cheap, so not treating fish for Ick shouldn't ever be
an issue. While aquarium salt is ideal, any non-iodized salt should
work fine as well.>
I think we noticed it on a Tuesday, and we bought the treatment on
Saturday and started administering it Saturday evening. One of the
female Black Mollies died the Friday before we got the treatment on
Saturday. So, by Saturday, we had 2 males and 2 females (Black
Mollies). We still had our 1 Oto (I believe female based on the fact it
immediately started going up and down the tank and across the tank
almost immediately after we got the heater to raise the temp to
<You can't sex Otocinclus this way.>
Websites also suggest this is the perfect temp for breeding Otos. (I
had no idea).
<Actually, Otocinclus should be kept fairly cool. They are extremely
sensitive to low oxygen concentrations, and as you hopefully remember
from school, the warmer water gets, the less oxygen it holds.>
As a side note, we also have lots of snails, and they have been
fruitful and multiplied. We started with 1 Black Mystery Snail (fully
grown) and about 12 baby snails (golden and black mystery mostly). Long
story, but we were wanting 2 or 3 babies, but we ended up with about a
dozen of them. Most of the baby snails died off (presumably
<Actually, Apple/Mystery snails do bad in aquaria. Don't keep
them with fish.>
Before we knew it, there were little specs above the water line. Our 2
airstones were moving water rather violently at the surface, and the
filter sucks in water, then pours it onto the surface. This was perfect
for the snails as they could put their eggs above the waterline and
they would constantly be wet by the popping bubbles. I suspect the Otos
also enjoyed the constant streams of current as well. By the way, I am
sinking every snail egg I find right now. Well, most aquarists would
have suggested that a new tank is the least likely scenario for fish to
breed. Not only did the snails breed, but the Black Mollies bred.
<As is their wont.>
One day I found a little fry at the bottom. I about had a heart attack
since I never even knew the Mollies were thinking of reproducing.
<I think "thinking" is over-egging the pudding a bit.
Males will inseminate anything vaguely Molly-like, and do so
persistently. In a 10 gallon tank, the females get stressed and often
miscarry, which you can recognise because miscarried babies are either
stillborn or so weak they fall to the bottom of the tank. Healthy
newborn Mollies can swim immediately after they are born, and
instinctively hide among floating plants *at the top* of the
I went to bed and prayed that it would survive.
<Prayer has it's place, I'm sure, but there are some more
immediate things you can do to keep Molly fry alive. Do read the above
By the next morning I wanted to save our little Molly and make it some
makeshift tank to keep it from being eaten. (Where there's a
redneck, there's a way). Keep in mind, that we are very financially
struck at this point.
<That's fine. Here's a tip: stick in some floating plants.
Floating Indian Fern is ideal, but even "goldfish weed" like
Brazilian Pondweed works well. The fry will hide there and won't be
eaten. Plus, floating plants give the female cover, and that reduces
the stress they get from amorous males.>
So, I found a casing that is used as a top to CD's. (if you go into
Wal-mart and state that you want to buy about 50 blank cd's You
will get a container that has a very large round lid. Since we still
had one of these containers, we simply took the lid off and turned it
upside down. It may not be large, but hey, it's what we can afford
for the little fry.
<Have done something similar myself. Use a screwdriver to punch a
few dozen small holes in the side so water can in and out, and so much
the better! If you don't do that, you'll need to change the
water in the container at least once a day.>
I went to find it and it was gone. I even moved the shell and gravel
around where it had been hiding the night before. We have about 12
large shells throughout the tank.
<Often what happens with very weak fry is they die, snails come into
the floating trap overnight, eat the carcass, and then the snails crawl
The gravel is a bit rough and not exactly ideal for fish tanks. I
feared it had been eaten. Several days later, we found one that looked
similar to it, hiding in the back. I believe it's the same one, my
<Molly broods can be anything up to 100 fry, though commonly
Either way, we caught it and put it in this makeshift tank I mentioned.
My wife got the idea that we should take one of the air stones out and
simply place it in the makeshift tank.
This seemed like a good idea at the time. I mentioned that it wont have
a filter or heater, but she doesn't have any idea how to solve
that. We put a shell in it too. The little fry loves to hide inside the
shell, or near the air stone. After trying to look through my daughters
binoculars backwards, I did see it fan its underside fin out showing me
that it is a female, because the males have a longer pointy fin in that
<You can't sex Mollies at this age. The males won't develop
their gonopodium until they're about 2 months old. Until then, they
look just like females.>
It is still too young to know for sure, but I believe it is a girl. So,
now back to the Otos, which is what I am really interested in. Since
the one Oto was trying to attract a mate, and there wasn't one, we
bought 2 more Otos.
<Not trying to attract a mate, trust me. These are SCHOOLING fish
and want companions.>
PetSmart didn't have any and hasn't in the few weeks since we
had bought the first one (the only one they had at the time). We had to
go all the way to Norman Oklahoma from Bethany Oklahoma just to get
Otos that day.
<I assume that's a long way'¦?>
None of the PetSmart stores has any in the greater Oklahoma City area.
So we went to "Wet Pets by Steve" in Norman, Oklahoma. We
bought 2 Otos (I wanted at least 1 male). When we looked at the Otos, I
was unsure how to tell the sexual differences in Otos (I just had some
very generic ideas from what I had read online).
<You can't sex them. Mature females become fatter when filled
with eggs, but that assumes they're sexually mature and
"conditioned". Specimens in pet stores won't have eaten
properly for weeks, so the chances of the females being ripe with eggs
are next to zero.>
The gist of the online info was that males are smaller and thinner. The
females are larger and potentially rounder. I noticed 1 Oto that was
certainly different that the one we had. If you could imagine a line
between the Otos eyes, and draw a triangle to its tail, that is what
our original Oto looked like. But this one was different, the triangle
only went down about half way down its body, then narrowed severely. It
was almost like it got pinched on the hind end. I figured this meant it
was a male, and the ones I am calling triangular are female. The little
guy was very active. We bought it, and another one that I believed was
female. I figured that if I bought 2 different ones, there would
definitely be at least 1 male and female in the tank.
<Actually, you need to get at least six of them for Otocinclus to be
happy. Forget about males and females. You can't sex them.>
When we acclimated them to the tank, I noticed that they were a lighter
color, they were smaller, and my wife noticed that our original Oto has
<More than one species in the trade: Otocinclus affinis and
Otocinclus vittatus are the commonest.>
The three of them do hang out quite often, but the one I believe is
male, is favoring the new female (not the original). None of them are
doing the chase and follow routine. I read online that Chinese Algae
Eaters are sometimes mistaken for Otos.
<You'd have to be legally blind to confuse Chinese Algae Eaters
with Otocinclus! They are completely different. Otocinclus are much
smaller, 1.5-2 inches, tops, Otocinclus affinis is grey above with a
thick black region along the midline of its body from nose to tail, and
off-white below. Otocinclus vittatus is essentially grey above, darker
grey along the flanks, with a thin pale band between these two grey
regions, and then off-white below. The Chinese Algae Eater
(Gyrinocheilus aymonieri) is more or less green all over with a few
bluey-green patches along the top surface and a distinctive zig-zag
bluey-green stripe along the midline. The Chinese Algae Eater is big,
fast-growing fish that gets to about 8 inches within the first year and
around 12 inches within the second. It is notoriously aggressive and
has no place in a community tank.>
I am hoping that we have 3 Otos. The littlest one (the one I believe is
male) is not afraid of the Black Mollies (as the others will get out of
the Black Mollies way when picked on). In fact, it even seemed to
attack the Black Molly who bothers it. This seemed very strange to me
for a tiny fish to stand up to and even fight back against a much
larger fish. The Black Mollies have learned to leave it alone.
<Hungry Otocinclus have a bad habit of rasping at the bodies of
other fish. They scrape at the body eating the mucous, but in the
process they create nasty wounds. Some fish learn to avoid them, which
could easily explain why the Molly seems nervous around them.>
The 2 new Otos are about an inch long (or slightly less). I believe our
original Oto is full grown, but still short of 2 inches (I have no easy
way to estimate its size). So, now on to the good stuff. Long before we
added the new Otos, I had performed a 50% water change. In the process,
we noticed a clear gel on the back of the filter. Not knowing what it
was, we tossed it out. I later, realized it might be Oto eggs. The
snails are all mystery snails and lay their eggs above the water line.
The Black Mollies are live bearers. The Neon Tetras died before even
the idea of multiplying. So by process of elimination, I figured the
gel had to be Oto eggs.
<Likely snail eggs.>
A quick reference on the internet confirmed this is a very likely
scenario. I eventually noticed 3 new areas of these egg gels. 1 of the
gels got scraped while trying to catch the Molly fry. I eventually
scraped the rest of it off the side of the tank where it was and let it
fall to the bottom. It seems I am finding several of these egg gels
now. I am concerned that our tiny male may not even be an adult yet
(and that our 2 females may have to continue to be "ladies in
waiting"). I noticed one of the group gels just disappear.
<They're snail eggs, likely from Physa or Physella spp. snails.
Even if you haven't seen them, they're in there. Fish eggs do
not look like clumps of jelly.>
It was truly strange, when my daughters came to visit, I clearly
pointed the new gel out and about 2 hours later, the gel was gone. I
suspect a molly ate it. That is one of my questions (Will Black Mollies
eat Oto eggs?). Next, some of them look ripped, as if something cut
them in half. Does this rip mean they hatched ?
<Sure, the snails hatch out within a few days.>
Could a snail have accidentally ripped it when it went over this gel ?
The snails are about the same size, or maybe slightly larger. I have
kept a pretty detailed "fish log" and it's kind of like a
diary of my observations in the tank. Apparently we started the tank
08/07/10 and added fish on 08/08/10. One phrase I used in my fish log
(after discovering the Black Mollies like algae tablets and algae on
the side of the tank and decorations) is "An Army of Algae
Eaters". Yep, every single fish in the tank loves algae. Could be
a reason why they thrive when using the 60 watt bulb until it burned
out and changed to a 100 watt bulb.
<You're using incandescent bulbs? I would not recommend this.
For a start, they're useless for growing plants, and they also
waste a lot of electricity. But they're also dangerous -- splashing
water on hot bulbs = explosion! If your hood has sockets for
incandescent bulbs, I'd STRONGLY suggest replacing the bulb with a
much cooler and less wasteful compact fluorescent
I was uneasy with the idea of causing that much algae. We still could
see green areas forming on the glass, but our army usually did a pretty
well job of cleaning it but couldn't clean it fast enough. We now
have a 15 watt bulb. I am concerned how much algae I need to
<Otocinclus starve quite easily; if they look "hollow
bellied", i.e., their bellies are concave, they're starving.
Algae wafers are good, but so is blanched lettuce, squished cooked
peas, sliced cucumber, sliced zucchini and cooked spinach.>
I dropped algae tablets in the tank and our original Oto never had any
thing to do with them. Our Black Mollies loved them. Once we added the
2 new Otos, I tried it again and they (the 2 new Otos) love the algae
tablets. So my biggest questions are concerning the Oto eggs. How do we
know if they were fertilized ?
<Snail sex is complicated. They're usually hermaphrodites. Some
species also have all sorts of fun stuff with 'love darts' well
worth reading about.>
How can we know if they are hatched (or damaged). Are the Oto fry good
enough at hiding for us to remove them before they get eaten ? And for
the strangest question of all.... would it be a bad idea to move some
of the Oto eggs to the tank the Black Molly fry is in ? Would she eat
the eggs ? Would she eat the fry ? She is still very small (I'm
guessing about 1 centimeter long). And finally How many Oto fry hatch
from an egg gel ? The gels themselves vary in size as it is. My wife
suggested that the gels might be mold. But they are clear.
<They're snail eggs!>
They look like they have white bubble specs in them. If we should try
to setup a third makeshift tank, how important is it going to be to
have a heater, filter, or airstone ? I'm sure they are Oto eggs
because as a test I ran room temperature water over our largest
ornament (a ceramic angel where the Otos love to hang out), and shortly
later there was an egg gel near the angel. The pictures I could find
online of Oto eggs are of 1 to 4 eggs and not a gel. I searched your
site, and nothing quite seems to cover these scenarios. But then again,
I may be a redneck, and things are always a bit different with
<Are they? Forgive this ignorant Englishman not really having a clue
what you're talking about.>
So, to make things clear, we now have 4 Black Molly adults (2 female
and 2 male), 3 Otos (I believe 2 females and 1 male), and several small
snails (the largest one died). In retrospect, maybe the little Oto was
protecting eggs I hadn't even noticed yet ? I sure hope it's
not a Chinese Algae Eater. I appreciate any and all help you can give
<I hope this helps. Cheers, Neale.>
Otocinclus, L134 Peckoltia; compatibility,
I recently returned from a 2 week stint working out of town to find my
5.5 gallon over run with the soft green algae that Otocinclus fish are
supposedly fond of. The tank was intended for another project which
didn't pan out (my Australe Killifish pair was living happily in my
29 gallon awaiting transfer but couldn't compete for food in my
absence and died after the first week.) I had been contemplating adding
four Otos to my already cycled 29 gallon and now I'm wondering if
the 5.5 would make a suitable quarantine tank or if it is too small
even for the short
<5.5 gallons is really not much good for anything except for a Betta
and/or small shrimps, and as you've observed, they are
intrinsically unstable and can easily flip into problem mode. You might
use it to quarantine very small fish, up to 2.5 cm/1 inch, but other
than that, I'd not risk stressing community fish species in such a
I removed the majority of the algae with a toothbrush but there is
still a fair amount in the tank.
<Algae removal will reduce the problem, but you do have to research
why it happened at all.
Without fail, algae comes back if conditions allow.>
There are a couple small plants (Cryptocoryne and some Alternanthera
reineckii clippings just floating) and some natural wood decor which
have been in the tank for 3 or 4 weeks. The tank itself has been set up
for just over a month, I used water from my 29 originally which I dose
with aquarium salt as a tonic about every second water change or
<Why use salt? The use of "tonic salt" is old school and
provides no real benefits.
Is this a reasonable place to keep four Otos for a couple weeks,
considering the small size and minor presence of salt?
<Possibly. But Otocinclus require somewhat cool, oxygen rich water
with lots of water current. Their mortality in "Nano" tanks
is depressingly high, despite their wide sale for such.>
I also wanted to ask whether my leopard frog Pleco which lives in my 29
is indeed a suitable tank mate for Otos or if I have been mislead.
<In a big enough tank with cool (24 C), fast-flowing water and ample
green algae, a school of 6 or more Otocinclus affinis/vittatus should
coexist with your L134 Peckoltia sp. catfish. Peckoltia spp. feed
mostly on the bottom and consume bloodworms and soft vegetables, while
Otocinclus graze almost exclusively on green algae from plant leaves.
So there shouldn't be much overlap. But L134 prefers warmer water
than Otocinclus, so they aren't an obvious or ideal combination.
Almost all problems with Otocinclus come down to keeping them too warm,
without enough oxygen, or without enough green algae. I doubt 50% of
the specimens sold last even 6 months.>
Your time and advice is greatly appreciated.
Should I move my Oto Cats? Sys.
Hi there, sure hope you can give me some advice.
<Will certainly try.>
Three days ago I added 3 oto cats to my 10 gallon aquarium, that they
share with a powder blue dwarf Gourami.
<Hmm... not wild about either of these species for casual aquarists
(forgive me for saying this if you're a serious aquarist who knows
all about them). Colisa lalia is notoriously prone to bacterial and
viral diseases, and an awful lot of them die quite soon after purchase.
If you've had this specimen a few months, then you may be fine. But
do research both Mycobacteria infections and something called Dwarf
Neither is curable, both are fatal, and in the case of DGIV, fully 28%
of the Colisa lalia exported from Singapore appear to be
Ammonia - 0
Nitrites - 0
Nitrates - 8
Artificial plants, not much algae
I allowed myself to be convinced by someone at the fish store that they
would be great companions to the Gourami, which may be true, however I
should have done the research first (doh!) because in hindsight, there
is not much algae in that tank, and there are artificial plants, not
<Well, plastic plants are not a problem here. They will soon become
covered with algae, and to a degree, the Otocinclus will eat this
algae. However, and this is a big "however", the types of
algae Otocinclus eat are limited to green algae and diatoms. They will
not eat blue-green algae, hair algae, thread algae or red algae. Green
algae in particular only grows in tanks with good water quality and
bright light. Such conditions are usually found in planted aquaria. In
tanks where the fishkeeper hasn't bothered with bright lights and
is using plastic plants, Otocinclus can starve to death.
I should point out that plastic plants and poor lighting isn't a
bad thing in itself, and indeed fish prefer poor lighting and usually
show their best colours in shady tanks. But in the case of Otocinclus,
it's not what you want.>
They don't appear to be eating algae wafers and I'm worried
they will not survive in that tank because of these factors.
<Do also review water temperature (which should be no more than 25
C) and water current (which needs to be brisk, ideally with extra
aeration). In short, not the same conditions as Dwarf Gouramis want.
Dwarf Gouramis like warm water, around 28-30 C, with a gentle water
I also have a 20 gallon aquarium, that includes 3 oto cats, 1
Farlowella, 7 Corys, 2 swords, and 8 black phantom tetras.
<Ah, now this is a tank that should be maintained quite cool, around
24-25 C, given the mix of fish you have. All these fish like a strong
current as well. So this seems like an ideal place for Otocinclus spp.,
particularly if brightly illuminated.>
Ammonia - 0
Nitrites - 0
Nitrates - 10
25% water change and vacuum weekly
Live plants, 2 large pieces driftwood, some visible algae
<Sounds a nice tank.>
Do you think I should move the 3 Otos that I put in the 10 gallon into
the large tank with real plants and more algae?
I'm worried that (1) My Farlowella will lose significant food
supply if there are 6 Otos present;
<A risk, but Farlowella should take algae wafers readily enough. You
can also supplement with sliced courgette and cucumber, and perhaps
strips of Sushi Nori (a good, cheap food for algae eaters generally,
and easily bought in Asian food stores).>
and (2) My 20 gallon will be overstocked (which you may tell me is
already overstocked without adding 3 more Otos!).
<Three Otocinclus will be neither here nor there. If nitrates are
this low, I'd actually be quite comfortable about adding the
What do you think?
<Go for it. Certainly more chance of success with them in the 20
gallon than the 10 gallon.>
Thanks so much!
Can and/or do Oto Catfish tolerate slightly
brackish water? 5/17/09
I put about a tablespoon of aquarium salt per 5 gallons.
<Why? Adding salt at this concentration does precisely nothing to
make your fish healthier or happier. Utter waste of money, and
potentially harmful to freshwater fish in the long term.>
If not, what small algae eating fish does well in brackish
<Best bets are Mollies and other Poeciliidae; algae-eating snails
such as Nerites; and salt-tolerant algae-eating shrimps such as Amano
shrimps. Most of the large herbivores like Scats will also eat
substantial amounts of
algae, though they're not normally used for algae control. As ever,
if you have an algae problem, the solution isn't fish but making
sure the tank is "balanced", in particular, that there are
enough fast-growing plants under strong light. Most algae problems
occur in unbalanced aquaria.>
Re: Oto Catfish and
brackish water? 5/17/09
Hmm that's weird because I thought that Mollies do best with a
little bit of salt...
<They do. One tablespoon per 5 gallons doesn't make brackish
water, and neither does it do anything useful for freshwater fish.
Adding such a trivially small amount of salt is pointless. Mollies do
well upwards of 6 grammes per litre, which is about one level teaspoon
per litre, and one litre is 3.75 US gallons, so that's about 3.75
teaspoons per US gallon. Since one tablespoon is three teaspoons,
that's a bit over a tablespoon per gallon. You're adding less
than a fifth the amount needed to optimize Molly health. In other
words, you're not doing much of anything. Plain vanilla sodium
chloride ("tonic salt" or "aquarium salt") as
opposed to marine salt mix (what you use in a brackish water tank) only
raises salinity, which has some therapeutic value in terms of nitrate
toxicity. Marine salt mix contains carbonate salts that buffers the pH
and raises the carbonate hardness, improving the stability of
conditions in the tank, and this also helps Mollies dramatically.
Bottom line, you cannot safely keep Otocinclus with Mollies: to create
conditions that Mollies need for maximum health and longevity, you need
to add more salt than you're doing now, and that would be harmful
to most freshwater fish, including Otocinclus. Trust me on this: I
literally wrote the book about brackish water fish! Cheers,
Re: Oto Catfish and brackish water?
Thank you much! I'm going to put some more salt in and look into
the Nerite snails... Thanks again
<Good-oh. Nerites work well in brackish water, especially Clithon
species; these eat a lot of algae! Cheers, Neale.>
Re: Oto Catfish and brackish water?
I went to my LFS and they didn't have any of the Nerite snails...
They just had "mystery snails."
<Not Nerite snails... Apple snails (Pomacea spp.)...>
I was told that they ate algae, but they were just sitting on the
<Eat some algae, but hopeless algae-eaters in most aquaria, being
happier eating plants or fish food... also very difficult to maintain
in the long term. Most specimens die within a year; need a resting
phase in cooler conditions for 2-3 months per year. Generally fiddly;
leave in the shop, or at least read up on Apple Snails first, e.g.:
I was able to test how salty my tank was and it was > 1.000 I'm
not sure what that means...
<Nor am I; "> 1.000" simply means more saline than pure
water... but that includes the sea! Apple Snails not tolerant of
brackish water, so not an option for the Molly aquarium. You're
after a specific gravity ("SG") of 1.002-1.003 for Mollies;
see WWM re: Brackish water fishkeeping:
I could add more salt and keep looking for those snails.
<Don't buy the Apple snails for this system.>
Just wondering: do Oto cats tolerate that?
I know they can be very picky when it comes to water parameters... What
do you think is best?
<For Otocinclus, you want low to middling temperature, around 23-26
C; you want soft to moderately hard water, so 5-10 degrees dH is about
right; and pH 6.5-7.5 is fine. Water turnover should be medium-high to
high, so say 6-10 times the volume of the tank in turnover per hour.
Water should be clean, and the tank well established. Green algae MUST
be present in the tank, or else provided via substitutes such as algae
wafers; Otocinclus DO NOT eat diatoms (the golden brown algae on the
glass); hair algae; brush algae; thread algae; or blue-green algae.
They are not compatible with Mollies or other fish that want hard
water, let alone brackish water. The majority of Otocinclus sold die a
few weeks after purchase simply because their needs aren't met. If
you don't have the right tank for them, don't waste your
Also, I was told that the Nerites were hard to find ??? Is that
<Not even remotely true in the UK; most good fish shops have them,
for around Â£1-2 a throw. In your own country may be
different; consult fishkeepers in your area. By far the best algae
Sorry for throwing all these questions at you.
Thank you so much
Otocinclus Hello Bob, have heard a lot about
you from folks at SDMAS here in San Diego. <Maybe see you later
tonight> My gig is working on breeding marine ornamentals but I saw
your article on the "little suckers" in FAMA and thought
I'd use the excuse to introduce myself. I had never head of the
fish until a few months ago, I helped a friend set up a fresh water
planted tank and came across them. Gotta say I love 'em. I have a
small backyard pond (300 gals) and was wondering how they might do in
there. Temps are in the high 50's right now, but I thought as
spring came on I could introduce some, maybe twenty or so. Do you think
they could handle So. Cal. temps year round if acclimated? <Not all
year round, no... could be kept outdoors maybe four, five months out of
the year... but would insert a thermostatic heater... set low... for
safety's sake> I've got some small Koi and pond comets (no
surprise) but what stuns me is that there are a number of zebra Danios
and white clouds that came in with "feeder" guppies I threw
in there during the summer. To my surprise the guppies died out as the
weather got colder in December but the zebras and white clouds seem
fine! I know you're a busy guy but if you have a moment let me know
what you think. ...David <These are tough little minnows. Have had
them outdoors (nearer the coast) in large enough, weather-sheltered
ponds in San Diego as well. Be seeing, chatting with you. Bob Fenner,
Otocinclus Meals Robert, <Hi, EJ, Sabrina
here tonight, instead> I read your article on Otocinclus on
wetwebmedia.com. Thanks. <Glad you enjoyed it! I'm
sure Bob appreciates the thank you greatly.> A couple
questions: In your article, you mentioned that they need
wood to survive. What kinds of North American woods are
acceptable for Otocinclus? <Pretty much anything
that's been *very* well cleaned and either sinks on its own or is
weighted will do. Check out your LFS for driftwood
ideas.> What state should the wood be in? Fresh,
weathered, decomposing, etc.? <Very well weathered - as
in, no bark remaining whatsoever. Wood that is decomposing
poses a problem as it will decay in the tank and make a genuine mess of
things.> What is a good brand of sinking pellets to feed
them? <Frankly, my personal favorite dry food brand is
Hikari, but I rarely (if ever) use algae wafers to feed my algae
munchin' dudes. Algae based frozen foods (Ocean
Nutrition's Formula Two, for one example) are a good prepared food
item to offer.> Will they feed on other vegetables besides the
spinach, Nori, and peas you mentioned? <Blanched cucumber
and/or zucchini, perhaps the soft insides of green beans.... some years
back, my Loricariids always appreciated the asparagus that I refused to
eat as a kid....> Thank you very much. <You
bet. Wishing you well, -Sabrina> EJ
Question Re: Oto placement
12/10/06 Hi Tom, <<Hey, Sean.>> I have another question
for you already. <<Let's hear it...>> I was at a major
chain pet store today, and much to my surprise, they were selling Otos
(Otocinclus) for $1.99. Since this is the first time I've seen them
in my area, and that price is too good to pass up, I bought 3 (I read
on WWM that they do well in groups). I have 2 tanks, and I can't
decide which one they would do best in. <<The quarantine tank,
Sean. (Being a little silly but I'll explain.) The store I buy my
fish from, my Otos included, is, literally, a 'Mom and Pop'
operation and won't sell their freshwater animals for the first two
weeks after they take delivery, i.e. they quarantine them all.
Saltwater fish are held for four weeks with cards posted on the tanks
showing the dates that the fish arrived at the store. That said, I can
guarantee that this isn't the case with your Otos. Point number
one. Next, Otos are notorious for being difficult to acclimate.
Wonderful little guys that they are, they're easily lost early on
no doubt due to the stress of transporting, handling, lack of
sufficient food and -- the big one -- means of capture. Because of
their tiny size and naturally tangled environment, many (most?) of the
Otos that reach the store have been taken in the wild using cyanide, or
other chemicals, to disable them for collection. (I would be skeptical
that 'tank-raised' Otos would be going for $1.99 each. Mine
were $3.99 each which I thought was a bargain.) The upshot here is that
these chemicals can remain in the internal organs of the fish either
shortening their natural lifespans of about five years or leading to a
much, much earlier demise. Darned hard on the Oto, to be sure, but if
one is lost and picked at by another fish, it, too, may end up with
contamination from the chemicals I referred to. Now, let's move on
to your options.>> Tank one is a 24g tall/show tank, moderately
planted, with a cheap "fizz tab" CO2 system. Its inhabitants
are 4 Opaline Gouramis, Trichogaster trichopterus (2 are the gold
variety), 2 paradise fish, Macropodus opercularis, 2 Ramshorn snails,
and one common Pleco, who will be re-homed soon as this tank will be
way too small for him (he's only about 4" right now).
<<Sounds like a good choice, Sean. And, I appreciate your
thinking regarding the upgrade for the Pleco.>> Tank 2 is a 5g,
moderately planted, with no CO2. Its inhabitants are 1 Betta and 3
cherry shrimp. <<Could be a good option as well but, personally,
I like to add some aquarium salt in with my Betta. Your Otos would
'tolerate' the amount of salt I use but I don't think
they'd appreciate it very much.>> Both tanks have laterite
and gravel substrate, a good amount of driftwood, and a pH just above
7. Neither tank has much of an algae problem, although both tanks have
small amounts of green "spot" algae. Now, here's my
question: which of these tanks would be a better fit for my Otos?
<<As you may have gathered, Sean, I like the larger tank for your
new pets. The smaller tank would likely work just fine but I'm not
a huge fan of keeping Bettas with other fish. Just me, perhaps. Also,
if you do decide to add salt to your Betta's tank down the road,
and I do recommend this, it probably wouldn't sit well with the
Otos if they were in the tank.>> Sean <<Enjoy your new
fish, Sean. Tom>>
What do I do with extra Otocinclus? 5/30/07
I have a 5 gal. Eclipse Corner Tank on my desk at work. There were 2
Betta's (with a divider) in it, but when I added 3 Oto's from
PetSmart soon after the Betta's died of tail/fin rot. I moved them
to separate bowls, and treated them but they died. I figured it was the
addition of the Oto's so I expected them to die as well. That
didn't happen. They cleaned my tank of all algae, and I feared they
would have nothing to eat because it seems they won't eat the algae
flakes. So, I went to my buddy's Cichlid tank and traded all the
ornaments (no, I don't know if this was a smart thing to do or not,
but I did it anyway). It seemed, that this brought new life to the
Oto's, as very soon after I spotted little white things on the
front of the tank. When I realized it was fry, I shut off the filter. I
counted about 12 fry stuck the glass. I turned to the internet for
advice and found little. I put a baby sock rubber banded over the
filter intake and turned that back on. Added an air pump for them. I
fed them boiled spinach leaves. Well, a spinach leaf from a coworkers
salad stuffed in a cup of hot water. They ate little holes in that
overnight. I do a 50% water change weekly, and slowly suck out the
leftover food every few days to keep the substrate somewhat clean. Now
I keep exchanging plants with my buddy's Cichlid tank for food and
they clean it overnight. There are now 4 or 5 baby's left and they
are half the size of the adults and seem to be doing fine. My question
is, what can I do with these extra Oto's? Can they go in the
Cichlid tank? Isn't that too much hardness for a Cichlid? Or can I
support 7 to 8 Oto's in a 5 gal tank? PetSmart told me that they
stock the same sex in the same tank and sell them that way so this
wouldn't happen. Well they screwed up and now I have these new
guy's. What do people do with their new fish when they didn't
mean or even know they would spawn? <Wow. This is quite an amazing
tale! On the one hand, a 5 gallon tank is really too small for
Otocinclus. As a group, Otocinclus are considered "delicate"
because they need good water quality and lots of oxygen. In most
community tanks, they tend to be short lived. But yours are doing well,
so well done! Anyway, as to where to put the Otocinclus. I personally
wouldn't mix them with anything other than, perhaps, South American
or West African dwarf cichlids. The problems are multiple. Firstly,
yes, they will not do well in Lake Malawi/Lake Tanganyika type aquaria.
Such hard and alkaline water conditions will not suit them at all.
Secondly, when kept with slow moving things like angelfish and discus
they tend to suck the sides of the bigger fish, scraping off the
mucous. I've seen this in my own tanks, with the Otocinclus rasping
away on large gobies, creating nasty blisters. Aggressive fish like
convict cichlids will simply hammer them to death. So ideally, give
them to someone with a peaceful community of other small fish such as
barbs and tetras. PetSmart cannot possibly sex Otocinclus so their
advice there was nonsense. In fact, breeding Otocinclus is quite
uncommon, so you've actually done rather well.> Tom <Cheers,
What is the best live plant for
Otocinclus? 4/19/08 What is the best type of live plant
for Otocinclus? I have two tanks, one 30 gallon and one 10
gallon. I just added two Otocinclus to the 10 gallon, which is 4
months old and has 8 molly fry, born two months ago. (As they
grow, I plan to move them to a bigger tank and only keep 2
mollies in the 10 gallon with the Otos.) I appreciate your site.
Thank you! <Otocinclus spp. couldn't care less about
plants, so use whatever you want. What Otocinclus need is green
algae (not diatoms and not hair algae). So provided you have 2
Watts per gallon upwards, plus lots of surfaces to grow green
algae (rocks, plastic plants, etc.) they will be happy.
Otocinclus spp. are not compatible with Mollies; their water
chemistry requirements are entirely different. Specifically,
Mollies more often than not need salt to do well and definitely
need hard, basic water conditions. Salt will stress the
Otocinclus, which need not-too-warm, oxygen rich water that is
soft and slightly acidic. There's no overlap really between
what the two species need to do well in the long term. Otocinclus
are extremely demanding, difficult fish, and the vast majority of
specimens die within months of import. Good luck,
Re: What is the best live plant
for Otocinclus? 4/19/08 Thank you for your help. I will
separate my Otos and my mollies. I am very new at this, and I
obviously have a lot to learn. :) <Glad to help. There is
indeed lots to learn, so buying a book before buying a fish is
always good advice. Remember, the guys in the pet store mostly
want to make sales! Good luck! Neale.>