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FAQs on Otocinclus Stocking/Selection

Related Articles: OtocinclusLoricariids

Related Catfish FAQs: Otocinclus 1, Otocinclus 2, & FAQs on: Otocinclus Identification, Otocinclus Behavior, Otocinclus Compatibility, Otocinclus Systems, Otocinclus Feeding, Otocinclus Health, Otocinclus Reproduction, & Suckermouth 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 Eaters


South American lime green Endler's- Oto?     7/25/16
Hi Neale,
I have a planted tank- see my large photo- of lime green Endler's. I have had it for a while and the population is now waning, down to 9 small fish.
I am debating whether to wait out till this population passes naturally, or add more fish since they could reproduce some more still.
<Understood, and been in this situation any number of times.
It seems like safest type to add would be more lime Endler's, but I was feeling like it might be nice to add a 2nd species for interest.
<A good plan. I gradually switched from Cherry Barbs to Limia in my big tank over the last couple years. The Cherry Barbs were "life expired" and now I'm down to a singleton living in the group of Limia. That Cherry Barb seems happy enough, with friendly company to help him feel secure, even in the absence of his own species. My point is that if you choose the second species carefully, there's no reason you can't phase in a new schooling species even as an existing schooling species dies off naturally.>
I read Otos or Cory's are ok with them, but Cory's are ruled out due to I have gravel and supposedly sand is best for their barbels.
<Correct. There are some midwater Corydoras though, like Corydoras habrosus, for which this is far less of an issue than it is with, say, Corydoras aeneus.>
They also suggested small tetras or Rasboras but seems like it could be a competition thing if adding a very similar type/style and its not as interesting if all the fish are little minnows, all looking the same other than their color.
<A question of taste really. Endler's Guppies will cohabit well with most "nano" tetras and cyprinids, assuming their water chemistry and temperature requirements overlap.>
I like this cute catfish "Otocinclus macrospilus" but they do get to 1 1/4", definitely larger than the little Endler's.
<But very peaceful. One of the standard Otos of the hobby. Don't like very hard water or high temperatures though, so while perfectly compatible with Endler's in terms of behaviour, and both species are primarily algae-eaters, they're not easily combined. I'd be aiming for around 10 degrees dH, neutral pH, and around 24 degrees C/75 F. Water current needn't be too strong given Enders are relatively weak swimmers, but Otos do need lots of oxygen, so air-powered filtration would be my recommendation. Failing that, just avoid overstocking, and perhaps add an airstone in summer.>
It's attractive and a different species so adds more interest, and larger looks nice. However, would the Otos be likely to compete with or be outcompeted for food from the Otos?
<Nope. Add Hikari Algae Wafers or similar, and they'll both nibble away happily. Otos really appreciate some fresh green algae, too.>
Would Otos trouble my longtime resident fish?
<Otos are good community fish, though as noted, they are quite picky about living conditions, and in busy, overstocked community tanks tend to die after a few weeks or months. In the right tank they're not hard to keep.>
Would the Otos eat the fry?
<Unlikely. Like most Loricariids, Otos will have minimal impact on livebearer populations.>
I think you said most would eat fry, just wondering how aggressively they would, since they are supposedly mostly vegetarian.
And should I feed cats algae tabs or will the algae on plants and rocks be sufficient nutritionally?
<Definitely add extra algae-based foods. Otos frequently starve if left to fend for themselves. They consume green algae and aufwuchs in the wild, but are not scavengers and they do not take hair algae, blue-green algae and so
on. Starved Otos will sometimes nibble on the mucous of large, slow-moving fish, but they're completely safe with fish their own size.>
I do want them to police algae aggressively, but I don't want them to starve to death if they are picky on the type of algae. I also have some crypts that I could transplant in there if this tank is not planted heavily enough for Otos.
<Otos actually like bright, open conditions best. Tall plants, flat stones, and plenty of places for them to graze, ideally with a decent current but at the least good quality, oxygen-rich water.>
<Welcome, Neale.>

Re: South American lime green Endler's- Oto?        7/26/16
Thanks Neale.
I will consider my options some more. I will test my water again. I can't. recall from last time what hardness is, but our water here is naturally very alkaline and hard.
<Endler's are good; do also look up Micropoecilia (some of which are extremely colourful) that are similar in size and behaviour. Phalloceros
caudimaculatus is another colourful little fish.>
I do have a log in there too that has an Anubias or something like that attached to it, and it could have affected the hardness.
<Unlikely. As I often point out, if softening water was as easy as dumping a log in it, we'd all be doing that! But unfortunately softening water requires either RO or the collection of rainwater. One is expensive, the other impractical in many places.>
If it's less hard or alkaline, I could always move the little Endler's to the 10 gallon which doesn't have the log since they're such a small number and prefer harder water, and try another fish for the 29 gallon.
<Cheers, Neale.>
Re: South American lime green Endler's- Oto?       7/26/16

Thanks Neale.
I will check those fish.
<Good luck! Livebearer associations can be a good way to find these fish, and they're often sold very cheaply at fishkeeping club auctions if someone is keeping them locally and has fry to spare. Cheers, Neale.>

Re: South American lime green Endler's- Oto?

Enough Otos now?     12/7/14
I have a tank rated for 29 gallons by the manufacturer. The tank is 36" L x 12" W x 18" H. The ph is 8 and nitrates and ammonia at 0. My filter is a sponge filter rated for 40 gallons. This tank contains 2 guppy females, 5 neon tetras, 11 platy fish, 1 Otocinclus catfish, and numerous bladder snails.
Just wanted to update you and let you know I got 2 more Otocinclus catfish for the one I already have in my tank. Is this considered a school of Otos now?
<A school is usually at least 6 fish. Smaller groups can work, but often don't. Otocinclus are difficult to keep in small groups. Indeed, they're difficult to keep at the best of times. I would keep at least 5, and ideally 7-8 specimens in a tank your size. Since Otocinclus are so tiny, they don't add a huge amount to the biological load on the filter. Keeping even 8 specimens wouldn't over-tax your aquarium. Ditto, to be honest, the Neons. Cheers, Neale.>
re: Enough Otos now?

Thank you Neale! :)
<Most welcome.>
Continuing Oto stkg   12/8/14

I have a tank rated for 29 gallons by the manufacturer. The tank is 36" L x 12" W x 18" H.
<Fun fact: 29 US gallon aquaria actually hold 25 US gallons on water. The aquarium sizes given are nominal and based on the outside dimensions, not the inside dimensions. The names of the tanks, 20 gallons, 55 gallons, and so on -- in US usage at least -- are purely a convention and have only a weak relationship to the amount of water they hold -- which is *always* less than the quoted volume. By the time you allow for rocks, gravel, etc., your tank probably holds a lot less water than you think.>
The pH is 8 and nitrates and ammonia at 0. My filter is a sponge filter
rated for 40 gallons. This tank contains 2 guppy females, 5 neon tetras, 11
platy fish, 1 Otocinclus catfish, and numerous bladder snails. Just wanted
to update you and let you know I am working on getting 5 more Otocinclus
catfish for the one I already have in my tank. Is this enough Otos now for
my tank? Is my tank overstocked?
<Your tank, once the Otocinclus are installed, sounds just about right to me, assuming, say, half of those Platies are juveniles. Bear in mind the Platies will breed quickly given the chance, so you want to be rehoming/selling Platies as you go along.>
Thank you.
<Cheers, Neale.>

Different types of algae and who eats/needs them?  (for miniature Otos)     8/26/13
Hi Neale, I hope you're enjoying your weekend! 
<Did indeed.>
I've attached 2 close up photos of some algae growing in 2 of my tanks. 
Since you've been keeping fish a long while, do you know what fish eats what type of algae....?
<In my experience, the "fish eats algae" paradigm is only of limited use, and tends to depend a lot on what other foods are available to the fishes in question. That said...>
In particular, do my algaes in these 2 pictures look like the type the tiny 1.5 inch Otos like to eat?
<Otocinclus tend to eat green algae and diatoms. Green algae is usually leaf-coloured and forms patches or low fuzzy tufts in aquaria. Diatoms form the golden-brown slime on glass and rocks. The dark green to blue-black beard and thread types are usually red algae (red is the colour when preserved in alcohol, by the way) and Otocinclus generally don't eat these types.>
Most store tanks are low on algae and therefore they just feed them pellets which is less ideal.
<Not sure this is strictly true; good quality algae flakes and wafers should make an acceptable staple.>
Since I grew some naturally with great success on this rock and the crypts plants, I wonder if I have an Oto buffet, or would they ignore it and grow feeble without some other food?
<Try it and see!>
I'm asking because in the forums I have heard people saying this fish eats this algae but not that algae, and they go on and on about their specific types of algae and the types that will or will not get eaten by various types of fish!!!
<Correct. There's some overlap between algae eaters, but each fish species often has preferences. I'd also add that few, if any, fish is as good as Nerite snails. Fish simply aren't as methodical. Fish generally ignore the thread or beard algae types too, with a few exceptions (Siamese Algae Eater and Ameca splendens spring to mind).>
I'd love to try a small school of Otos, but I want to make sure I have the right type of algae so they're not just stuck with compressed tablets of algae.
<Do bear in mind that Otocinclus aren't just eating algae; to a large extent they're feeding on detritus and tiny animals that live among algae threads, what scientists call "aufwuchs". So, even if the algae type isn't 100% right, it'll still be home to stuff Otocinclus can eat.>
Every fish care paper I read says "it's best to have natural algae growing in their tank," but that's not specific as to what type the species actually prefers and will eat.  I suspect what I have is good Oto food....but don't know for absolute certainty if these are super picky little creatures.
<They're semi-picky. They are at risk of starving in a new aquarium or one with dim lighting and hence little algae growth beyond, say, blue-green algae (which they cannot eat). But in a mature aquarium or one with enough lighting for plants to thrive, they'll find enough to eat, especially if their diet is supplemented with a good quality algae wafer. Generally, competition from other fish tends to be the killer. If they're harassed by larger fish, then they'll fail to thrive, no matter what other factors are correct.>
If I move the sword(or swap rocks) to the 2nd tank, they could have the rock with the heaviest algae, since there will be more of them.  Though they're so little... Not sure even they could make a dent on the furry rock any more than the sword has.  Of course maybe if they had just the plants and the less algaeful rock, maybe they'd clean those up faster.  That would be nice for the plants.
And the sword favors the rock.  She munches it happily.....I feel a little guilty to move it to the other tank.  Is the algae on the rock probably the same type as the algae growing on the plants anyway?!
<Otocinclus and livebearers enjoy the same algae types, so whatever the Swordtail eats will be correct for the Otocinclus.>
And....would I need to supplement the Otos diet with anything else if this is the right type of algae for them?
<For sure, though less often (once a week, perhaps) if they are nicely fattened up on algae and detritus.>
I do intend to put a piece of driftwood in their tank as well, as I heard they like it.
<Correct, though likely this has more to do with culturing algae and aufwuchs than anything else.>
Thank you, I hope you've kept Otos to know what they like too.
<Yes, have kept them, though much prefer Nerites as algae-eaters.>
I know you like brackish a lot, which they're not, but I think you have wide knowledge and experience.
<Cheers, Neale.>

Re: Different types of algae and who eats/needs them?  (for miniature Otos)     8/26/13
Thank you, Neale, very helpful.
I like the little Otos and I'll get some. Have a nice week.
<Most welcome! Neale.>

Oto Pics please?   2/9/10
Hello, Sorry to bother you guys again... but could you send me a picture of a healthy and an unhealthy Oto? bottom and side view is best. All the images on the web seem the same and I'm not good enough to tell them apart.
<Do see here:
As with other Loricariidae, healthy Otocinclus have convex bellies; unhealthy ones concave bellies. Very ill fish have sunken eyes. It's a simple as that. I don't really recommend Otocinclus for casual aquarists because they are delicate, need specific foods, and tend to be short-lived in "average" aquaria lacking the oxygenation and water flow they appreciate. Cheers, Neale.>

Betta Eye Problem, & Otocinclus sel. f'   02/06/09 I bought my Betta about a year ago. He is housed in a 10 gallon planted tank that he shares with 4 Otos. I keep the temp at 78. The tank has medium lighting (2 x 13 watt spiral CFLs) that is set for 10 hours a day. I use a sponge filter and do weekly water changes of 20%. For food he gets Betta pellets with occasional freeze dried blood worms and brine shrimp mixed in (all Hikari products). He occasionally munches on Oto algae wafers but spits most of it out. The problem: My Betta has one white spot on each eye. The spots have been there about a week, unchanged. The spots are opaque and on the lower half of the eye. His eyes are not cloudy and the spots are defined, not cottony, and it looks like they are on of the lens of his eye. He does not show any sign of distress. He's eating normal, normal behavior, normal eyesight it seems. The water parameters are all good, ammonia 0, nitrites 0, nitrates 5. Last PWC 20% on Sunday. When viewed under a magnifying glass, I can see no swelling, redness, or movement of a parasite. Do fish get cataracts? Could this be early signs of blindness? I have attached a picture in the hope that it will help you diagnose the problem. Thank you for taking the time to read my email. Heidi <Hello Heidi. Firstly, well done on keeping your Betta in a heated, filtered aquarium of reasonable size! If only everyone did that, there'd be a darn sight fewer sick Bettas in the world. Now, do fish get cataracts? If we simply mean, can the clear parts of the eye get damaged or turn opaque, then the answer is yes. There are two main reasons. The first is physical damage. If a fish bumps into something, or repeatedly jumps out and hits the hood, is handled in a rough net, or is molested by some other fish in the aquarium, the front of the eye can get damaged, and the net result is the equivalent of scarring. Dead white tissue forms a lump at the front, obscuring vision. The second reason is infection, where the damage is caused by bacteria or a parasite (e.g., Eye Fluke). More often than not, this follows on from chronically poor water conditions, with bacteria getting into the fish and causing harm because the fish's immune system has been weakened. Now, I don't think that's the issue here because your tank sounds very good. Otocinclus are much more sensitive to water quality than air-breathing Bettas, so if the Otocinclus are fine, the Betta should be too. (As a side note, I'd not recommend keeping Otocinclus in tanks 10 gallons or smaller precisely because they are so sensitive to water quality.) There are some less common reasons eyes become cloudy. One is malnutrition, specifically a lack of Vitamin A. Again, I don't think that's the issue, since the diet you're offering sounds excellent. Another possibility is chlorine, which will cause this symptom among others if not removed from the water. Assuming you're using a dechlorinator, then this isn't likely. This leaves two possibilities we can't do anything about: genetics and senility. Bettas *are* inbred and genetically quite weak, and there are lots of problems that they get that aren't obvious when young but become more serious as they age. As for senility, wild Bettas are basically annual fish. Since the fancy Bettas sold in shops are about six months of age, your fish may well be a year-and-a-half old already, if not more, if it was sitting in the aquarium shop for a while. So it could be just plain old. Sure, Bettas can live in aquaria for 2, 3 or more years, but anything over a year from purchase and your fish is well past its prime. Can anything be done? Not really; just as in humans, damage to the eye doesn't usually heal without surgical or pharmaceutical intervention, and that's not really viable here. Since fish don't rely on their eyes to anything like the degree humans do, if its vision is impaired, it will manage just fine using its other senses, particularly its "built-in radar" system, its lateral line. The one thing I would keep alert for is how the Otocinclus behave. I have (repeatedly) seen these fish attack injured fish, going for open wounds and grazing on the blood. They may even cause these wounds directly. Personally, I do not consider Otocinclus community fish, and particularly warn against moving them with anything slow, e.g., Angels, Gouramis, or indeed Bettas. Cheers, Neale.>

Re: Betta Eye Problem  02/06/09 Neale, Thank you so much for your prompt reply! It seems likely from your description that either genetics or senility is to blame. As I said, he does not seem to be bothered by the condition, but I will certainly keep a close eye on him. I appreciate your advice about the Otos. I was told by a trusted Betta website that Otos would be ok with Bettas. To date, I have not seen them attack my Betta whether he's been sick or healthy. They generally stay away from him, as he likes to chase them away from his territory. However, I will be much more alert to their behavior towards him since I trust your experience in the matter. If I see that they are giving him a hard time in any way, then I will find them a new home. Thanks again, Heidi <Hello Heidi, I'm glad your Otocinclus are behaving themselves. Some do, but some don't, hence my warning. Good luck, Neale.>

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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