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FAQs on Callichthyid Catfish Selection

Related Articles: Callichthyid CatfishesSummer loving: cats in the garden, kittens in the kitchen by Neale Monks,

Related Catfish FAQs:  Callichthyids 1, Callichthyids 2, Callichthyid Identification, Callichthyid Behavior, Callichthyid Compatibility, Callichthyid Systems, Callichthyid Feeding, Callichthyid Disease, Callichthyid Reproduction, Catfish: Identification, Behavior, Compatibility, Selection, Systems, Feeding, Disease, Reproduction,

Almost all Callichthyids, Corydoras are social animals... Must be kept in groupings to be happy, healthy.  

A golden albino Corydoras aeneus at the 08 Interzoo.

Quick question about Corydoras catfish 5/11/10
<Hello Judy,>
I was just wondering if it is harmful to keep just one Corydoras catfish?
<"Harmful" is a difficult word to use here. Yes, these are schooling catfish, and if kept singly the loner will be stressed and therefore more likely to get sick.>
I have a 10 gallon tank with 6 Neons and one Corydoras. Is one alone stressed out since they are so social??
<Yes. Get four more of the same species!>
Thank you!
<Cheers, Neale.>

Angelfish Mating/Cory Cats Schooling 8/20/09
Hello Crew, Hope all is going well. I have a question, please. I have a 75 gallon fw tank with 6 medium sized angelfish. I have read that if 2 pair off for mating they can get aggressive towards others in the aquarium.
Does this mean that they have to be removed or is a 75 gallon tank large enough so that the others can still live in peace?
< The pair will defend the eggs and fry. As the young become free swimming and began to wander their territory will expand. I would let them breed in the 75 gallon tank first and see how it goes.>
I also have a question about Corys. Right now I have 6 pandas. I have read that the more there are the more they will school and the minimum number should be 6. But if I purchased 3 or 4 of another type I know they would not school with the pandas, but will usually stay with their own kind.. But when there is less than 6 of a certain type of Cory can they still be happy together in the smaller groups even though they won't school? Thank you for your help. James
< If they want to school then they will form their own little group regardless of the species. They will probably join the pandas if they really feel threatened.-Chuck.>

Cory Catfish, sel., fdg.  2/7/09 I am thinking about adding a couple Cory Catfish to my tank of livebearers. I was wondering-do Cory Catfish eat fish waste? I know they eat leftover food... Thanks a bunch! <Hello Hannah. Corydoras (and indeed catfish generally) do NEITHER of the things you mention. No, they do not eat fish waste. Why would they? Waste is removed by your filter, and through water changes. Every additional fish you add INCREASES the amount of ammonia and faeces in the tank, so your filtration will need to be adequate to the task. Secondly, they DO NOT eat (just) leftovers. Catfish should be given sinking pellets -- catfish food -- at least 3-4 nights per week. Corydoras are nocturnal fish by choice, and during the night will eat the pellets without having to deal with competition from day-active fish in the aquarium. Besides catfish food, they enjoy algae wafers and frozen bloodworms. One last thing: Corydoras are SCHOOLING fish, and are not happy in groups of less than 5 specimens. Adding "a couple" is simply condemning these adorable little fish to a nervous, unhappy existence in your care. Since tank-bred Corydoras such as Peppered Corydoras and Bronze Corydoras cost very little, there's really no excuse for not getting at least 5 specimens. If your tank is so small (or so heavily stocked) you can't add 5 specimens, you probably should add 2 either. Five specimens will settle just fine into a busy 20-gallon community tank without complaint. Cheers, Neale.>

Freshwater Stocking Question, Corydoras and Platy Sel.  11/26/08
Hello W.W.M. Crew!
I am trying to help some friends with their aquarium, and would appreciate some stocking advice. Here is the setup: They have a 20 gallon aquarium, that is 24 inches long. It has ordinary (non-calcareous) aquarium gravel, with plastic plants, and is filtered by a Hagen AquaClear, that turns the water over 7 or 8 times per hour. I have that filter stocked with Hagen's bio-ceramic media and synthetic filter floss. These ladies follow proper procedures for cleaning the filter and doing weekly, partial water changes.
They vacuum half the substrate each month.
<I'd do this every week or two>
They also know how to feed properly, without over-feeding. Their tap water comes out of the faucet at ph 7.8, and is hard, but not VERY hard.
(I can't recall the dh numbers right now.) They use Cycle on their tap water, and allow it to sit for three days before placing it into the tank.
This tank and filter are already "mature"/cycled, as it has been up and running for a year, with some other fish. (Those fish will NOT be in the tank, though, with the new fish.) After much consideration, trying to agree on fish that would be interesting for them, but appropriate for the water conditions and size of the tank, we have agreed that they will stock with Corydoras and female platies. So here are my questions: If they stock five Corydoras, then how many platies would be the most that they should stock,
<A dozen or so... A comment re the all female selection. Very likely some individuals here will reproduce... these and many other livebearers are able to "store" sperm in their tracts... So, unless isolated from males at a very small size...>
and are there varieties of Corydoras that should be avoided, because they will not adapt, (as well as others), to the hard water?
<There are some that are better than others... you could do the LONG read on fishbase.org re the genus' constituents known natural ranges here... Or "just shoot for" tank-raised species/specimens... as all these will "stretch" to this pH, not too hard water>
Their water parameters will be kept at healthy levels, but I am concerned about things such as "psychological space/crowding" for the platies. Also please tell what you believe the IDEAL temperature would be for this mix of
species. Thank you, so much, for what you do! Have a great, fishy day!
Jake D. (Wisconsin)
<And you as well Jake. Bob Fenner>
Re: Freshwater Stocking Question 11/26/08

THANK YOU, Bob! And I would like to tell you, quickly, that it is because of YOU and the W.W.M. website, (and the effect that it has had upon how I keep fish), that I originally stepped forward to ASSIST these ladies, when their tank looked like a failed chemistry experiment, and they were about to leave the hobby. It has been a privilege to be able to help them to succeed, and to remain in this great hobby/pursuit. I continue to look for opportunities to assist others in a similar way. THANK YOU, one hundred times, for all that you do. Have a blessed Thanksgiving! Jake
<Ahh Jake, deeply gratifying. So glad to find ones efforts inspiring others to help. Cheers, Bob Fenner>

Cory Cats, sel.   10/17/08 Hi, I know that Cory catfish are schoolers, and I plan on buying about 10 of them over time. Do they all have to be the same species or will they still stay together if they are different? Thanks, James <A few species are known to form mixed species schools in the wild. But in the aquarium they don't school unless they're all the same species. The main exception is the Albino Corydoras, which is (usually) the Peppered Corydoras (C. paleatus) and consequently these two catfish will school together. That said, Corydoras look best when it's a big group of the same species. Cheers, Neale.>
Re: Cory Cats  10/17/08
Thanks Neale, and do you feel there is one particular one species that is the most attractive? <Depends on the tank. If it's warmer than 26 C, then your best bet is the excellent Corydoras sterbai. Otherwise at the 22-26 C most Corys prefer, some of the best species include Corydoras julii, Corydoras elegans, and Corydoras panda. In subtropical tanks, Corydoras barbatus (properly, Scleromystax barbatus) is just stunning. Sadly it cannot be kept in tropical tanks.> Also, if I do not get all of the same species but mix them up, even though they will not school will they still be happier together than if there were only one or two? <Different species don't form schools, so if you must mix them, get six of each species. But seriously, big schools of a single, schooling species look really nice. I have nine Corydoras paleatus in one community tank and eight Aspidoras pauciradiatus in another. Watching them swarm about, with the males flirting in front of the females, is great.> Thanks again <Cheers, Neale.>

6 Cory Cats, comp./sel.  4/13/08 Hello WWM crew, Thank you for your wonderful site and service to the community. We have a "community" 125 gallon tank working fine. Our tank has a total of 9 Corys: 2 albinos, 5 bronze, 1 peppered, 1 c. metae, along with the usual swords, mollies, and platys. Specific question on the usual advice to have 6 or more Cory cats. I use six as an example only. Please clarify whether this means they must all six be the same type (say, 6 emerald or 6 peppered); or does it mean 6 of any type Cory, as we have? <While a few Corydoras species will mix in the wild, for all practical purposes they should all be treated as different things when it comes to forming schools. So six bronze Corydoras, six peppered Corydoras, and so on. While they may all look the same to us, to one another they are completely different things. The sole exception is the Albino Corydoras, which is (usually) Corydoras paleatus, i.e., the peppered Corydoras though sometimes it is alternatively the bronze Corydoras, Corydoras aeneus.> We ask because none of the Corys (including the 5 emerald cats) hang out together as a "shoal" like the photos on www sites. <Precisely so. You need a reasonable number, generally six or more.> Ours are all independent critters. Is this normal or is it due to our large tank (5' long, 18" wide) ? <Bit of both. Corydoras don't normally swim as a single group all the time. They often cleave off into subgroups, often a couple of males escorting a mature female. Mine do this all the time, and periodically you'll find eggs laid on the glass as evidence. Remove the eggs, rear the fry (comparatively easy) and add them to your group of Corydoras!> One observation is that the new (this week) C. metae immediately paired off with the 1 peppered Cory; but neither of these "hang" with the albinos or emeralds, and the albinos do not associate much with the emeralds. Does this mean we have stocked wrongly? <"Wrong" is perhaps too strong a word, but perhaps not "ideally". It's a lot of fun to watch Corydoras doing the social thing, and if you feel you have space in your community tank, I'd heartily recommend bumping up the numbers. In 125 gallons, you could easily keep ten of each and not have problems.> We want to do the right thing by these very nice fish. <Indeed so!> Many thanks, Rosemary <Cheers, Neale.>

Re: 6 Cory Cats  04/14/2008 Neal, brilliant reply in concise terms. Off to the LFS Monday for some albino and bronze Corys! Many, many thanks! Rosemary <Happy to help. In theory at least, Peppered and Albino catfish should school together; if they don't, then the chances are you have Albino Bronze catfish rather than the more common Albino Peppered catfish. Enjoy your fishkeeping! Cheers, Neale.>

Cory Help... sel., hlth.   2/1/08 Hi! I have recently bought one albino Cory for my 20 gallon aquarium. Along side the Cory in the tank are 3 marble mollies, a balloon molly, 2 white fin tetras, and a zebra tetra. <No such thing as a "zebra tetra" -- do you mean a Zebra Danio? Small minnow with longitudinal gold and purple stripes.> My problem is my Cory is acting extremely weird. He swims up and down radically and never stays in one spot too long. Sometimes he just frantically swims around and around in the aquarium. I feed him using fish flakes and sinking pellets. But it seems as though he doesn't eat this food. I have had him for 4 days now. Could he be acting strange due to the presence of the other fish? Or is there something else that could be a contributing factor to this? <He's lonely, scared, and miserable -- and likely wondering why he was bought by someone who doesn't research their fish first, usually an omen of doom for unfortunate fish. Corydoras are *schooling* fish, and have to be kept in groups. Four is the minimum really, and you need six or more to see them at their best. So go to your retailer and buy some more. Albino Corydoras are usually Corydoras paleatus, so you can mix them with regular Corydoras paleatus (known as "peppered Corydoras" in the trade).> Sincerely, Michael <Cheers, Neale.> <<Well done Neale. RMF>>

Corydoras... sel.  10/27/07 I'm trying to decide how many Corydoras (trilineatus) I could put in a 55 gallon tank. It will have only a 6" passive female Severum in there besides the Corydoras. The Severum has been living with 6 Cory Cats for quite some time now and they do excellent together in a 45 gal tank. I really want more Cory's (such gentle & sweet little fish!). I do daily partial water changes and the 55 gal will have 2 Emperor 400 Bio-wheels on it, my water quality is great. Would I be over-crowding 'space-wise' if I had a total of 20 Corydoras in this 55 gal along with the Severum? I value the opinion of all your volunteers very much but am scared enough of crowding them that I'd love to have your opinion. Thank you so much for your time and efforts. Mitzi <Mitzi, what you propose should be fine. The thing to do is add them a batch at a time though, so the filter can adjust. Maybe 5 at each go, wait a few days, and then add 5 more. While you're waiting, check the nitrite level to make sure the filter has adjusted, and if necessary, wait for nitrite to reach zero before adding any more. Realistically though, mature filters adjust to extra fish within a day or two. You also want to optimise each filter; i.e., remove pointless stuff like carbon and Zeolite, and make sure you're using the best quality biological media available. One problem you will have is feeding this number of catfish without the tank getting over-polluted. Check the nitrate level every week or so for the first month or two, so get an idea of how quickly the nitrate level rises and how often you need to do water changes. While Corydoras are fairly indifferent to nitrate, Severums, like all other cichlids, are very sensitive to nitrate over the long term, developing things like Hole-in-the-Head. Good luck, Neale>
Re: Corydoras, sel.  10/28/07
Neale, <Mitzi,> Thank you for your opinion and (as always!) good suggestions. I'll do as you suggested. One of the Emperor 400 Bio-wheels is already cycled so that should help a lot. <Indeed. A mature filter will mature an immature one connected to the tank very quickly, especially if you divide out the mature filter media between the two of them.> It's funny you mentioned carbon as being "pointless". Carbon in filters is one of my personal 'pet peeves' and I never use it. I slit the blue 'carbon' cartridges that come with the filters and fill them with those little rough stones they sell for filter media. <Sounds ideal. The cartridges are basically a marketing ploy, like razor blades, to make you spend more for something cheap purely because it "fits" the device you have. In reality, practically any filter can be fiddled around with to accept generic media, be it ceramic hoops, filter floss, crushed coral or whatever.> My water stays crystal clear. <Water quality has very little to do with carbon. Water changes will dilute the organic acids that stain the water, while water changes and careful siphoning will remove solid wastes and silt. No fuss, no muss. Water changes really are the KEY to fishkeeping, hence my argument that fiddling about with softened water and the like if you live in a hard water area is pointless if it means you can't afford to do large, regular water changes.> It's so much easier to cycle a new tank by just taking a cartridges out of one of the filters on a cycled tank and putting it in the new one. <Indeed. It's called "cloning a filter" and works very well. Once you have one mature aquarium, you never need to cycle any of the new ones you buy afterwards.> I've been feeding the current Corydoras those sinking carnivore pellets plus they eat the crayfish chunks, bloodworms and the variety of food the Severum gets. I couldn't ever get the Severum to eat her 'greens' until I put the Corys in there. Since then she shoots right over there and snatches veggies up like she thinks the Corys are going to eat it :-) <Sounds like typical Cichlid behaviour. Cichlids are like children: they want whatever is on someone else's plate, on the assumption it's better than what they have on theirs! I think its this sort of quirky behaviour than makes cichlids so popular with aquarists.> The Cory's will pick at veggies every once in awhile but I seriously doubt the Severum has anything to worry about. <Corydoras, in the wild at least, actually eat substantial amounts of algae and decaying vegetation. It's certainly a good idea to use vegetarian flake and pellets periodically. Both the Corys and the Severum will benefit from this.> Thank you! I'll be looking forward to my little "Cory Community". Mitzi <Sounds good. Enjoy. Neale>

My poor catfish!! Corydoras dis., use     8/22/07 Good morning, we are fairly new aquarium owners, we have 2 gravel cleaner Corydoras and one of them has a very swollen belly, we thought it might be pregnant but today it is finding it very difficult to swim and keeps going to the surface. Sometimes it falls back down to the bottom like its dead but then will swim back up. Not keeping it's balance very well. The other one looks fine and is sat on the bottom as normal. Please could you give me some advice on what to do. I can't seem to get a clear enough picture but will try if you really need one. They are a grey colour with a pinkish tone, about 2 inches long. Thank you so much Sharon <Hello Sharon. Corydoras aren't "gravel cleaners" -- that's your job. Indeed, forcing catfish of any kind to root about dirty gravel causes infections to set in, typically associated with eroded barbels (whiskers) and, in serious cases, reddish sores on the belly. A photograph will help, but my assumption without one is that your catfish are suffering from poor water quality. In a new aquarium the ammonia and nitrite levels quickly reach toxic levels. Catfish will try and mitigate the problems by gulping air, which is the dash to the surface your catfish are doing, but eventually the ammonia and nitrite cause damage to the fish, which is the odd behaviour. Even in the short term, prolonged exposure to nitrite and ammonia will kill them. Using your test kits (which I hope you have!) ensure the ammonia is 0 and the nitrite is 0. If this is not the case, do a 50% water change. Repeat the water test and, if required, 50% water change every single day until you get 0 ammonia and nitrite for two or three days on the trot. At that point, you can scale things back to 50% water changes per week. Cheers, Neale>
Re: my poor catfish!!   8/22/07
Thanks for the reply, the poorly one has got a red sore on his belly. The other one is fine, sorry about the gravel cleaner thing, that's what we were told at the shop we bought them in and we certainly don't force them to feed from the bottom and we clean the gravel with a suction thing (haven't quite got the hang of that task properly yet!!) Can't get a decent photo as he is laying on his back at the back of the tank but is still moving. Water test levels are as follows ammonia and nitrite are at 0ppm ph levels are slightly high at 7.4 and nitrate is in between 0 and 5 ppm. Tank is about 3 months old now and we have a variety of fish including mollies, tetras, a Betta, Plecos, silver shark, clown loaches and one of our guppies has just given birth to 18 fry ( which are in a nursery tank) all other fish are fine we have only lost two Tetras (one zebra tailed and one gold) since we started. Thanks Sharon <Water chemistry/quality sounds fine. pH 7.4 is perfect for Corydoras. Your selection of fish is a bit random though, and likely to cause problems in the long term. I personally don't like keeping Corydoras in tanks with gravel; they are much happier in tanks with sand. But clean gravel shouldn't cause Corydoras to die. Do check the water quality once or twice more today. Ammonia and nitrite can "spike" after feeding, while dropping down to zero a few hours later. Also check the other fish for signs of problems. If they're all healthy, I'd be tempted to just sit back for a month and not add anything new to the aquarium. Leave things be. Only afterwards, once you're happy the sick Corydoras was "just one of those things" consider adding more fish. Cheers, Neale>
Re: my poor catfish!!   8/22/07
Hi again, I think the poor little thing has finally given up the ghost and has passed away, I have read these are social fish so should I go and get another partner in case the one left gets lonely!! Any other advice would be greatly received. Thanks again for all you help so far Sharon <Corydoras do indeed need to be kept in groups, but I personally wouldn't add anything else to your tank for another month. Let things stabilise, and get a sense of how the tank is working out (or not, as the case may be). Ultimately, keep at least four Corydoras, preferably six. Ideally all one species, but they do often mix quite well, so you could get three of one kind and three of another. Cheers, Neale>

Unsure of fish choices   - 4/7/07 Hey everyone! <Hello!> I love the website and it has been very beneficial in helping me set up my 45 gallon tank... thanks for all the info! I have a few questions I was hoping you could answer for me. <Okay...> First off, I understand the importance of a quarantine tank but does it have to be a tank or can it just be a bowl? <No; really. A quarantine tank has to be a reasonably healthy environment. If it makes the fish more stressed and more sickly, it isn't really doing its job.> See, I'm back to college and inherited the tank after my grandparents moved (it's a fairly new tank) and can't really afford to go out and purchase a large tank. Would a quarantine bowl be sufficient or no? <Fair enough. Lots of people are stuck with using just one tank. It's not optimal, but its workable. Just choose stock carefully, don't take risks, look out for the first signs of sickness or aggression, and be prepared to implement a "Plan B" if things go wrong, i.e., have some anti-Whitespot remedy to hand, and check with your retailer if you can return aggressive fish.> Secondly... <Yes...?> My tank has been running for a few weeks now and I have slowly been adding fish. <Define "few weeks" and define "slowly".> Currently, I have 5 zebra Danios and 4 sunburst Mickey mouse platys. <A pretty safe combo.> I would like to add more but am unsure about what fish to add. <I tend to go with one inch (or centimetre, if you're metric) of fishes that live at the top to every two inches of midwater swimmers to every one inch of bottom dwellers. This gets a nice balance of activity at all levels of the tank without making things to crowded. In this case, I'd recommend Corydoras catfish as being about the right size to fit in nicely with your fish as well as being easy to obtain and coming in a variety of colours. Peppered and bronze Corydoras are "old reliables", but you might go with something a little more elite like Panda Corydoras or Leopard Corydoras if funds allow. There's a nice intro here: http://www.wetwebmedia.com/FWSubWebIndex/callichthyids.htm and you will find any number of books and web sites about "Corys" if you look for them. Corydoras vary in ease of maintenance, but most are pretty robust and all are peaceful and happy to eat dried foods. Some species will spawn in aquaria, and if you remove the eggs and place in another tank (or even a breeding net) rearing the fry isn't all that hard but extremely rewarding. Baby catfish -- "kittens" -- are truly adorable. Keep in groups, ideally at least 3, but preferably six or more. They don't like deep tanks: no more than 30 cm/12", because they are air-breathers and cannot swim up too high. Keep the sand/gravel clean because dirty conditions at the bottom of the tank can cause problems such as eroding whiskers. One last thing: contrary to popular belief, these fish won't live on leftovers, they need their own food. Ask your retailer for catfish food, and use according to the label.> It seems like every fish comes with a problem... either too aggressive or too high reproductive rates. I don't want to end up with a tank full of 60+ guppies! What fish should I purchase from here? <Corydoras are about as problem-free as any aquarium fish can be. Small (most are around 4-6 cm in length), utterly benign towards other fishes, and generally resistant to disease, they even wink at you! Personally, I'd recommend peppered Corydoras if you've never kept catfish before. Peppers are usually cheap and easy to find, and probably the most forgiving of all Corydoras in terms of water quality and other problems.> -Victoria <Cheers, Neale>

Looking For Pygmy Corys   6/27/06 Hello crew, Where can one obtain a pygmy Cory in America? The links I have found are only in the UK. Thanks in advance, Lisa S. Immarco <They come in to the US. I saw some at a wholesaler a few weeks ago. They are very inexpensive and so not too many breeders work with them. Check out Aquabid.com or try the chatroom at planetcatfish.com.-Chuck>

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>>

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