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FAQs on Otocinclus Selection

Related Articles: Otocinclus, Loricariids,

Otocinclus
Bob,
I read your article in FAMA re: Otocinclus/S. American sucker mouth catfish..., and purchased 2 at a local pet shop. The salesperson said they were Chinese catfish, but they looked like the Oto pictured in your article. I want them for algae control in a 36 gallon tank with 3 mature Angel fish---2 egg laying females, and one male. I chose them as they seem to be more active than the Pleco species, and because they will make an "active" addition to the tank. Any suggestions...? Thanks. Dale Fox
<Mmmm, suggestions re what? Enjoy them. Maybe give a read over the materials on the Freshwater sub web: http://www.wetwebmedia.com/FWSubWebIndex/fwsubwebindex.htm
Bob Fenner>

Cycling, timing, and Endler's
Dear WWMites,
<<Kewl. I'm an official Mite!!>>
Well, thanks to the rest of your site (and I thought I'd read nearly everything before), I've answered my own questions.  Wow, y'all have a lot of stuff for us to read!  I backed out to the home page and found more links to more info a bit farther down.  Unfortunately, the intense absorption of so much info knocked most of the third grade out of my head to make room.  Ah, well, third grade was a bust anyway...  To recap:
We'll get the Otos much later in the process rather than earlier, and our earlier decision on five (one per ten gallons) is apparently a good population.  Also, my bride and I decided we're going to replace several of the silk plants with live plants, both for the beauty and the Otos.
<<Excellent idea :)>>
We'll stick with making larger batches of tweaked water, and go get a cheapy air pump to aerate it (at least overnight) before we use it.  We're also talking about increasing the water changes to 20% a week rather than every two weeks, especially after reading about the sensitivity of Otos and Corys to nasties in the water.
<<It would be a good idea to vacuum your substrate regularly, Corys are prone to bacterial infections of the barbels. Nasty stuff can accumulate in gravel beds, and Corys are always sticking their noses into...it. :P>>
We're going to have to decide which Corydoras to get, since they prefer being with their own.  I'd had the impression that it wouldn't quite do to mix based on genus rather than species.  (Now if I can just convince my wife to go with the paleatus...)
<<My favorite Corys are melanistius melanistius and adolfoi. You can check out pics of any species of Cory cat at www.planetcatfish.com/ Maybe you will both see something inspiring there that you agree on :)>>
As I said in an earlier message, the little speed demon is, indeed, an Endler's.  He's started getting a stronger hint of green on his caudal fin, and a more definite green tinge on his rear half.  We're looking forward to getting a group of them after New Year's.
<<Nice fish. Easy to keep and not a royal pain like so many livebearers can be...Belonesox spring to mind.>>
Again, thanks for the wonderful site, and I hope I haven't chewed up too much of your time.
Glen
<<You are most welcome. Happy Fishing. LOL.
-Gwen>>

Oto <what? Oto parts?>- 6/1/07
Hi Robert,
after days of hunting for Oto's I feel that it can not hurt to send you a mail.
<Hello, Neale here.>
> I am in Shanghai and now have a discus aquarium. In Europe I have always had Oto's in my tanks and have always been fascinated by their behaviour and rewarded by their gentleness. Clean plants no algae growth on the leaves etc.
<Yes, they can be excellent algae eaters. But I hesitate to recommend them too widely for a variety of reasons, not least of all the fact they seem to travel poorly and the mortality immediately after import is very high.>
> Plenty of algae (green) on the back wall of the tank but not a problem.
<Your observation of their liking for green algae is spot-on. Otocinclus are ideal for planted aquaria where the background level of algae is low and limited to green algae types. In "unbalanced" aquaria with few/no plants, Otocinclus have no useful impact and in fact often starve to death because they will not eat the brown, hair, and blue-green algae common in such tanks.>
> I have hunted everywhere to try and purchase these fellows here in China
> but have had no success.
<Given you are keeping discus, I would *never* keep Otocinclus with them. I have observed Otocinclus sucking the slime from large, slow fish in my aquaria, and assume that discus would be an obvious target. Other aquarists have observed this, with Otocinclus attacking angels and discus. Far better to choose something a bit large, like one of the "clown" Panaque species (such as Panaque maccus) or even Ancistrus spp.>
> I am hoping that with your knowledge of these fish and your reference to the tiger Oto that has been bred in Asia that you may be able to point me in the right direction to obtain them. I have always had the Otocinclus affini but any
> Oto's would be fine.
<I personally don't know who is importing/trading that variety, but I'm sure if Bob does know, he'll follow up. As a general rule, placing a "special order" with retailers is often the way to go. I've done this many times.>
> I apologise if this mail is out of context as I have no idea how busy you
> are or how much mail you get from your site.
> kindest regards
> john Ramsey
<Good luck, Neale>

Question for Neale about TFH article, 10 gal. stkg. Otos f' 01/13/2008
Neale,
<Hello Evan,>
I read your article in the TFH about 10 Gallon stocking. I was wondering if you had a reason for not mentioning Otocinclus along with the Corydoras. Is there a specific reason to not add the Otos to a 10G tank or were you just limiting yourself to keep the article concise?
<Yes, there was a specific reason for leaving them off: Otocinclus spp. have an abysmal track record in aquaria generally, the VAST majority dying within a few months of introduction. I would never recommend them to anyone without several years of experience, and even then, only when placed in a mature tank (lots of green algae/aufwuchs) and excellent filtration. This pretty much rules out the average 10 gallon tank received as Christmas present, which was the focus of the article. If you want an algae-eater, get cherry shrimps; if you want a catfish, get Corydoras hastatus or some other Dwarf Corydoras. Both these will prosper without anything more than an "average" level of care, i.e., water changes, proper food, etc.>
I ask because I have a 10G with 9 Glowlight Tetras to which I would like to add 3 or 4 Otos (as soon as LFS orders some).
<Think very carefully about this, and only if you have LOTS of green algae. Otocinclus really don't eat anything much besides green algae and the microorganisms therein. Brown algae, blue-green algae, etc. aren't substitutes! To get green algae growing, you'll need 2 Watts of light per gallon, at least. There needs to be a "turf" of green fuzzy algae on the plants and rocks. THAT'S what these little catfish eat. On top of that, you need plenty of water flow (at least 4x the volume of the tank in turnover per hour, and ideally 6+) and above-average oxygenation. Nitrates need to be close to zero, and certainly less than 20 mg/l. If you can't answer all these demands, then skip Otocinclus.>
I perform 40% WC every 5 days, so I think I would be able to keep that many fish and maintain good water quality. What are your
thoughts?
<Best avoided, frankly.>
Thank you,
Evan
<Cheers, Neale.>

Re: Question for Neale about TFH article plus Corydoras 1/14/08
Dr. Neale,
<Evan,>
Thank you for your responses to my questions about Otocinclus. Through my web-based research I thought that supplementing the Otos' diet with Nori and vegetables would be adequate, so I'm very grateful for your input on the matter.
<You may be fine doing precisely that, but the cold, hard reality of the matter is that whatever people do, most Otocinclus don't seem to survive long in anything other than a big, mature tank with plenty of algae. Their diet is a subject of some discussion among hobbyists. They may be partly parasitic as well as algae-eaters: in aquaria they have been reported MANY times to eat the mucous and skin from large, slow fish. I have seen this myself, my Otocinclus causing a significant amount of damage to the body of an Awaous goby. Do they eat mucous only when hungry? Is it something they do regardless? No-one really knows.>
On the subject of the Corydoras hastatus & C. pygmaeus: I currently have medium to large "aquarium gravel" (colored pebbles) up to about 1cm in diameter. Would this substrate be acceptable for keeping either of the above Corydoras species?
<Acceptable yes, ideal no. With all Corydoras, the best results come with lime-free sand, simply because it's more fun to watch them plough through the stuff. That said, the midwater Corydoras species like Corydoras hastatus likely don't care either way.>
If not, what kind of substrate do you recommend?
<The best for a small, planted tank is unquestionably black sand. Looks lovely, and because it removes upwelling light, fish adopt their brightest colouration.>
If I need to replace the gravel, what is the best method?
<If you have an undergravel filter in your tank, best not to change the gravel at all. But if the gravel is purely decorative, there's no real problems. Just take all the fish out, put them in a tub or bucket with the filter connected to that vessel so the bacteria stay happy. Then empty out the aquarium, remove some or all of the gravel, and then add the cleaned sand to a depth adequate for the plants. If no plants (or at least no plants with roots, as opposed to epiphytes) then you only need 2 cm/1 inch of sand.>
Again, thank you for your help.
Evan
<Happy to help, Neale.>

How to keep bacteria alive in a fishless tank? 4/24/08
Hello Neale,
<Giuseppe,>
hope you and your tanks are doing well.
<Yep, we're all just fine; thanks for asking!>
I have 2 unrelated questions.
1) I will be on vacation for 2 weeks in June and I was wondering if the good bacteria would starve to death in a tank without fish. By then I will have all my fish in the 46-gal, but I would like to keep the established 10-gal running to try breeding when I'm back. Again my question is whether or not the good bacteria would starve in these 2 weeks or not and what could be a solution. Maybe I should leave 1 or 2 Otocinclus and they would eat the algae in the tank?
<Otocinclus aren't my favourite fish in the trade because their survival record is so poor. But certainly some hardy algae eater, like an Ancistrus or Hemiloricaria whiptail, could be left in the 10 gallon tank for a couple of weeks with a bit of carrot for grazing but otherwise left to fend for himself. Alternatively, just stick a small frozen prawn in the tank and let it rot away. Remove when you get back, obviously. Yet another option would be a plain "holiday block" of the type often sold for Goldfish and the like. These are basically lumps of limestone that dissolve away, releasing flakes of food. Again, the food will rot, producing ammonia. The bacteria couldn't care less where the ammonia comes from.>
2) How should I feed Otocinclus? I used to have 1 in the 10-gal tank and he did great for 1 year without feeding anything. When I moved the fish to the 46-gal it died after a couple of weeks, probably because there was no algae in the tank. When I'll be on vacation for 2 weeks I will use an automatic feeder loaded with flakes or mini pallets, which the Otocinclus wouldn't eat. Do you think the poor guy would starve?
<Otocinclus are very difficult to feed. They almost entirely eat "aufwuchs", the combination of green algae and micro-invertebrates that encrust surfaces in bright, clear waters. They are opportunistic to some degree though -- most notoriously eating the mucous from slow moving fish -- but still, getting enough food into them within a community setting can be very hard. They do best (perhaps only do well) in large tanks with established algae "turfs" on the rocks and plants where they can feed continuously, supplementing that diet with bloodworms, algae wafers, and so on. I'd tend to avoid in favour of hardier, more adaptable Loricariidae, of which there are many.>
Thanks,
Giuseppe
<Cheers, Neale.>

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 = 6°, GH = 12°. 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.>

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