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FAQs about Ariid Catfishes, aka Columbian, Silver-Tipped-... "Sharks" Behavior

Related Articles: Marine, Brackish & Freshwater Catfishes (Columbian, Silver-Tipped, Black Fin... "Sharks") of the Family Ariidae by Bob Fenner, Columbian Shark Catfishes and other Ariidae by Neale Monks,

Related FAQs: Ariid Cats 1, Ariid Cats 2, Ariid ID, Ariid Compatibility, Ariid Selection, Ariid Systems, Ariid Feeding, Ariid Disease, Ariid Reproduction, Marine Catfishes, Catfishes in General

Behave differently in different settings, with different tankmates.

Re: Black Fin Shark, beh.    8/20/10
Thank you so much. The information is extremely helpful. Do they sleep?
<Naturally, like all fish. Groups rest up together in the corner of the tank. Unlike most catfish, Sciades are active during the day as well as the night, so they tend to take catnaps throughout the 24-hour cycle.>
Thanks so much,
Nicki
<I assume this catfish isn't in a 1-gallon tank anymore. Cheers, Neale.>

Strange Behaviour from My Columbian Sharks (Arius seemanni), and BW plants   3/20/10
Hello,
<Hello,>
I have a 60g Tank that is set up as brackish. The salinity is about 1.008
<I don't think this can be the case. At SG 1.008, Java ferns and other plants would be dead. Here's the best approach: weigh out the marine salt mix first, and then use your hydrometer to check the specific gravity. On
my web page there's a little program called Brack Calc that tells you how much salt mix you need for a certain salinity at a certain temperature.
http://homepage.mac.com/nmonks/Programs/brackcalc.html
For SG 1.008, you'd have to be adding 12.8 grammes of marine salt mix per litre at 25 degrees C (1.7 oz per US gallon at 77 degrees F). There's about 6 grammes of marine salt mix per level teaspoon, so we're talking 2 teaspoons per litre; that's quite a lot of salt mix. Many folks get reading hydrometers completely wrong, so weighing the salt out first is a good way to get roughly the correct salinity, and from there you can fine-tune your ability to use a hydrometer.>
and pH, nitrite, nitrate, and ammonia levels are normal; temperature varies from 29 - 31 degrees.; I have to small pieces of driftwood with attached Java Fern and another type of brackish plant.
<"Brackish plant"? Never seen anything like that on sale. What plant are you talking about here? My concern here is that because there are no brackish water plants sold explicitly in the trade, if you have freshwater plants, then your salinity cannot be nearly as high as you think it is.
This in turn leads to the most obvious conclusion here that if salinity is too low, Colombian Shark catfish won't be happy, and most behavioural abnormalities they exhibit come down to this issue.>
This other plant I am not sure of type it is; it has long light green leaves that are fairly thin and the stem leads into the leaf. They look very similar to the Java only lighter and thinner (I've searched and cannot find a name for them and the manager of the LFS where I purchased them is not in for another week).
<Hmm... doesn't ring any bells, I'm afraid. A photo would help.>
On one side of the tank I am using a lighting that is made specifically for fish while the other side is plant/fish. I have a Castle Decoration that is about a foot tall that is used for hiding.
<For the most part, Colombian Sharks don't hide. They live in estuaries in large groups, and rely on schooling for defence.>
I was originally doing about a 10% water change every week and it was suggested that I should be doing at least 25%. So I did a 50% change and the last change was 25%.
<Yes, 25% every week or two is a good idea.>
After letting the tank cycle for about 3 weeks
<Generally not long enough to fully cycle the tank; I'd expect non-zero nitrite levels, and these will stress your catfish.>
I purchased 3 Colombian Sharks, about 2 months ago (I am planning on upgrading the tank to 150g as they get bigger). For the first month or so they were very active, eating normally, and schooling together. They were about 2.5" and now are just over 3". About a month ago they became Lethargic. This was around the time I added the plants but I have never heard of plants effecting sharks in this way.
<Actually, Colombian Sharks are very easily spooked, and adding things that clutter up the bottom of the tank can cause them a little upset. Best to make sure there is ample swimming room, and keep decorations along the edges. But I still think salinity and/or water quality are the issues here.>
Two of them spend time in the light green plants and one of them hides in the castle. The two that hide in the plants are a very, very light silver compared to when I first purchased them and the one in the castle is almost black in color.
<Stress.>
They are still eating actively and at night they still explore the tank but not quite as enthusiastically as normal. If I leave the light off during the day they are a bit more active but not by much. They also seem to be more territorial with each other, even at night.
<They will get over this in time.>
There are no growths or fungus that I can see and they are not rubbing on any of the decorations. I also purchased 3 Sailfin Mollies and they are doing fine and are very active. Is it possible that it is just the plants that are causing the issue?
<Unlikely, but I'd remove the plants anyway, since they won't be happy at the salinities required in the long term.>
and if not what can I do to help my sharks?
Thank You Very Much for All Your Input.
<Cheers, Neale.>

Columbian sharks acting very strange...  2/18/10
Hello!
<Hello,>
I am an owner of 2 Columbian sharks that I have bought about 3 months ago.
<Nice fish. Often badly maintained, but in the right tank, very pretty and peaceful. They are highly sociable though, so I'd recommend keeping at least three. They do grow quite fast, and will eventually get to about
20-30 cm/8-12 inches in length. Wild fish are supposedly a bit bigger.>
I bought them from a small tropical fish store where the owner seemed to be very helpful to me as to setting up the tank.
<Good.>
The sharks are about 4 1/2 in. now and have been in brackish water the whole time.
<Define "brackish water" for me. I ask because some people think it means adding a teaspoon of salt per gallon. It does not. In broad terms, these catfish are more marine than freshwater fish, so they need quite a lot of salt to do well. Juveniles are fine around the SG 1.005 at 25 degrees C mark, or about 9 grammes of marine salt mix per litre (about 1.2 oz per US gal.) but specimens above half adult size will need about twice as much salt, around SG 1.010, or 15.5 grammes marine salt mix per litre (about 2 oz per US gal.). Let's be clear about how much salt this is. One level teaspoon of marine salt mix weighs roughly 6 grammes, so even at the low end, that's 1.5 level teaspoons per litre. There are 3.79 litres to the US gallon, so that's about 5.7 teaspoons per US gallon, or a little under 2 tablespoons per US gallon. In fact you shouldn't just be weighing or spooning salt mix this way, but using a hydrometer as well to check the specific gravity. A basic floating glass hydrometer costs around $5, and used properly, is perfectly adequate for this sort of fishkeeping.>
The owner of the store told me that I do not need to keep track of the pH levels as long as I change the water once every month, which I have been doing consistently.
<Hmm... in general, yes, if you do regular water changes, pH changes should be relatively minor. If you're using adequate marine salt mix -- not tonic or aquarium salt -- then again, pH should be controlled automatically by
the carbonate hardness in the marine salt mix. But monthly water changes aren't generally recommended. It's better to do weekly water changes around 20-25%, wherever possible.>
Recently, I bought an algae eater fish to go into the tank because the algae was becoming a problem. It has been doing fine.
<If you have an algae eater in this tank, you ARE NOT adding enough salt.>
I also had an Ick problem, but just recently cleared that up.
<If Ick/Whitespot can live in this tank, you ARE NOT adding enough salt.
Salt is used to treat Ick, so the sheer fact you had Ick at all implies the salinity is far too low.>
I feed them 1 cube of frozen blood worms a day, and they seem to like those very much.
<Yes they do, but they need a more varied diet. Add good quality catfish pellets to the mix, plus a variety of seafood (cockles and strips of white fish like tilapia being especially nutritious). Prawns and mussels are enjoyed, but these contain a lot of thiaminase, so should be used sparingly.>
Just when I thought my sharks are nice and healthy, they start to act very strange.
<This is a VERY hardy species that usually survives all kinds of disasters, but it's behaviour is a very good clue to its unhappiness.>
They are both continuously swimming forward towards the glass and won't stop until they eat. Sometimes, one sits in the bubbles(from the oxygen making thing) under the heater. That one also likes to go in a corner and put his nose in the corner of the tank while swimming straight up. Is this regular behavior? Or are they sick??
<They're trying to migrate downstream, towards the sea. Make sure the tank is salty enough, big enough, and equipped with enough water current for them to feel at home. For a trio of specimens, I'd be looking at a 350
litre/75 US gal. system with a robust filter rated at not less than 8 times the volume of the tank in turnover per hour, and ideally more current than even that. The specific gravity should be at least 1.005, which is lethal to freshwater fish like Plecs and Gyrinocheilus "loaches", so remove the algae eater. If you want algae eaters in this tank, a mix of brackish water Nerites and large Sailfin Mollies will do the trick nicely.>
Thank you for your time!
-Carlee
<Do try to get a look at my brackish water book. Your local library should be able to get a copy, even if you don't want to buy it. There's a whole chapter about brackish water catfish. Cheers, Neale.> 
Re: Columbian sharks acting very strange...  2/18/10

To answer your answer of the brackish water, the place I got them from told be to put 1 tablespoon of non iodized salt per gallon, do I need to increase the amount?
<Yes. Read my message, It'll tell you how much MARINE SALT MIX to use. Not non-iodised salt, tonic salt, aquarium salt or cooking salt. Marine salt mix, as you'd use in a marine aquarium. This is crucial, because brackish
water isn't brine. It's not water with a bit of salt added. It's a mix of freshwater and seawater, and the marine salt mix doesn't just add sodium chloride but also alkalinity and pH buffers. It's very different stuff.
Goes without saying that adding enough marine salt mix to make Colombian Sharks happy will stress/kill any freshwater fish and plants. Remember, these catfish are marine fish that tolerate freshwater for a while. Not
freshwater fish at all. Cheers, Neale.>

Strange Behaviour from My Columbian Sharks (Arius seemanni), and BW plants   3/20/10
Hello,
<Hello,>
I have a 60g Tank that is set up as brackish. The salinity is about 1.008
<I don't think this can be the case. At SG 1.008, Java ferns and other plants would be dead. Here's the best approach: weigh out the marine salt mix first, and then use your hydrometer to check the specific gravity. On
my web page there's a little program called Brack Calc that tells you how much salt mix you need for a certain salinity at a certain temperature.
http://homepage.mac.com/nmonks/Programs/brackcalc.html
For SG 1.008, you'd have to be adding 12.8 grammes of marine salt mix per litre at 25 degrees C (1.7 oz per US gallon at 77 degrees F). There's about 6 grammes of marine salt mix per level teaspoon, so we're talking 2 teaspoons per litre; that's quite a lot of salt mix. Many folks get reading hydrometers completely wrong, so weighing the salt out first is a good way to get roughly the correct salinity, and from there you can fine-tune your ability to use a hydrometer.>
and pH, nitrite, nitrate, and ammonia levels are normal; temperature varies from 29 - 31 degrees.; I have to small pieces of driftwood with attached Java Fern and another type of brackish plant.
<"Brackish plant"? Never seen anything like that on sale. What plant are you talking about here? My concern here is that because there are no brackish water plants sold explicitly in the trade, if you have freshwater plants, then your salinity cannot be nearly as high as you think it is.
This in turn leads to the most obvious conclusion here that if salinity is too low, Colombian Shark catfish won't be happy, and most behavioural abnormalities they exhibit come down to this issue.>
This other plant I am not sure of type it is; it has long light green leaves that are fairly thin and the stem leads into the leaf. They look very similar to the Java only lighter and thinner (I've searched and cannot find a name for them and the manager of the LFS where I purchased them is not in for another week).
<Hmm... doesn't ring any bells, I'm afraid. A photo would help.>
On one side of the tank I am using a lighting that is made specifically for fish while the other side is plant/fish. I have a Castle Decoration that is about a foot tall that is used for hiding.
<For the most part, Colombian Sharks don't hide. They live in estuaries in large groups, and rely on schooling for defence.>
I was originally doing about a 10% water change every week and it was suggested that I should be doing at least 25%. So I did a 50% change and the last change was 25%.
<Yes, 25% every week or two is a good idea.>
After letting the tank cycle for about 3 weeks
<Generally not long enough to fully cycle the tank; I'd expect non-zero nitrite levels, and these will stress your catfish.>
I purchased 3 Colombian Sharks, about 2 months ago (I am planning on upgrading the tank to 150g as they get bigger). For the first month or so they were very active, eating normally, and schooling together. They were about 2.5" and now are just over 3". About a month ago they became Lethargic. This was around the time I added the plants but I have never heard of plants effecting sharks in this way.
<Actually, Colombian Sharks are very easily spooked, and adding things that clutter up the bottom of the tank can cause them a little upset. Best to make sure there is ample swimming room, and keep decorations along the edges. But I still think salinity and/or water quality are the issues here.>
Two of them spend time in the light green plants and one of them hides in the castle. The two that hide in the plants are a very, very light silver compared to when I first purchased them and the one in the castle is almost black in color.
<Stress.>
They are still eating actively and at night they still explore the tank but not quite as enthusiastically as normal. If I leave the light off during the day they are a bit more active but not by much. They also seem to be more territorial with each other, even at night.
<They will get over this in time.>
There are no growths or fungus that I can see and they are not rubbing on any of the decorations. I also purchased 3 Sailfin Mollies and they are doing fine and are very active. Is it possible that it is just the plants that are causing the issue?
<Unlikely, but I'd remove the plants anyway, since they won't be happy at the salinities required in the long term.>
and if not what can I do to help my sharks?
Thank You Very Much for All Your Input.
<Cheers, Neale.>

Surfacing Columbian sharks and feeding 11/29/09
Hey Bob, SmallIslander here,
<Hello,>
I am over in the Turks & Caicos Islands and while we have the best beaches, we don't have a pet shop. I am new to aquariums and have started off with a 55 gallon (will get a bigger one eventually) with 3 Columbian Sharks and a host of a lot of other fish that I believe are all brackish water fish.
<Sounds fun.>
I have a fresh water tank and the exporter who sold and sent me the fish said to add salt. I added about 23 teaspoons. (they seem to be doing better, should I add more? How much more? Is that enough?
<A "teaspoon" is a pretty meaningless amount. One level teaspoon is approximately 6 grammes (this is easiest in metric, so you'll have to go along with me on this). Full strength seawater is 35 grammes per litre, or slightly under 6 teaspoons of marine salt mix per litre. Colombian sharks are happiest in middle to full strength seawater, so something around three teaspoons per litre of water is what you need. If you visit my web site, there's a little program called Brack Calc that can be used to convert between metric and gallons, should you prefer to work that way.
http://homepage.mac.com/nmonks/Programs/brackcalc.html
So, your tank is 210 litres in size, and you're adding 23 teaspoons. That's 0.11 teaspoons per litre, less than one-three hundredth of the amount of salt in seawater. A trivial, indeed useless, amount. You could drink water with that salinity and come to no harm.>
Can you tell me why my Columbian sharks keep surfacing in front the water filter, is it that they like the current?
<This is "normal" behaviour under the circumstances. It is the nature of Columbian sharks to migrate up and down rivers. In aquaria, they tend to swim close to the filter, presumably because the water current is strongest there.>
I am not sure about the water as I should have a test kit by Wednesday. But I treated it for a few days before the fish cam with tap water treatment and Nitraban balancer. Another problem is that I thought the sharks would eat the tropical flakes. .. not at all.
<They will eat catfish pellets, but they do need a mixture of wet-frozen foods as a staple. Chunks of white fish fillet, prawns, mussels, squid and so on all work well. Some mullet species contain thiaminase, so you have to be careful here. Do read this article before planning the diet:
http://www.wetwebmedia.com/ca/volume_6/volume_6_1/thiaminase.htm
A mix of wet-frozen seafood plus some good quality catfish pellets should balance things out without too much bother.>
I have tried shrimps from the grocery store and frozen mullets. NO luck yet. I had them from Friday and they haven't eaten. Everybody else did. My last problem is one of the sharks seem to have a busted eye (its white as if he hit it on the aquarium or decoration inside. I don't think he can see out of this.
<A common reaction to clumsy handling. Damaged skin on the outside can improve on its own assuming the eye itself isn't damaged.>
Also I noticed his belly has shades of black light dots, can this be his normal skin?
<Yes.>
What do I do? Another shark has a bloated belly but all are swimming healthy. Should I add Epsom salts?
<No. You need to be adding a lot more marine salt mix. This will take care of general hardness, carbonate hardness, and salinity all at the same time. I'd start at 9 grammes/litre (SG 1.005 at 25 C) for now, to give your filter some time to adapt to brackish conditions. After that, you can nudge the salinity up across a few months to wherever you want to maintain it. Do read some of the brackish water articles here at WWM or on my web site; you may also find either my book or Frank Schaefer's Aqualog book on the topic worthwhile.>
If so how much. When to I add the algae control?
<Don't.>
Thanks. This is the best site online.
<We like to think so.>
SmallIslander
<Cheers, Neale.>

Columbian Shark... beh... gen.... no ref...!?  4/27/2009
Hey crew! Hopefully you can answer my question... I had a Columbian shark for the last two weeks.
<Sciades seemanni, a fantastic fish. But remember, it's a SCHOOLING BRACKISH WATER fish, and cannot be kept either singly or in a freshwater aquarium.>
As any Columbian shark we was very active going always up, down and around my tank. He was about two inches long. Yesterday I woke up to find my shark very slow, barely moving, kind of sad :( He didn't react to the food I threw him nor Anything I did for him.
<Oh dear.>
I went to the pet store were I bought him, the guy told me to change 50% the water.
<What is the salinity of the water? Sciades seemanni needs at least SG 1.005, and adults do best at anything between SG 1.010 and fully marine conditions.>
I did everything as careful as I could. I even changed the filter.
<Why did you change the filter?>
It's frustrating because I woke up this morning to see him dead! The strange thing is his dorsal fin was RED. I mean, RED! don't exactly know what that means... Did I poison him?
<We're you keeping him in a brackish water aquarium?>
Was he eating enough? Don't know! What does the red fin means?
<Could mean all sorts of things, but typically a secondary bacterial infection brought on by poor water quality or the wrong water chemistry. I cannot stress how important it is that these fish are kept in big aquaria (55+ gallons) with very powerful filters (they need strong water current) and a reasonably amount of salinity.>
I know he wasn't being bother by the other fishes, I had him black pebbles, sand under the pebbles, couple of plants, strong current, new filter even a really cool air pump thing, jeje, lots of the common suggestions....
Where I failed...?
<These fish are very hardy in brackish water aquaria; they cannot live in freshwater aquaria.>
Help me please... I think I want another one.
<Schooling fish, must be kept in groups: three or more specimens!>
He was the star of my tank... :(
<Yes, these are spectacular fish, and in big brackish water systems "steal the show".>
Sent from my iPhone ;)
<Sent from my Mac.>
Joanne M.
<Cheers, Neale.>

Shark Catfish... beh., fdg.    Hello, <Ave!> I just bought two shark catfish, they are completely silvery with lots of black spots. <Sounds like these are in fact the Pictus Catfish -- Pimelodus pictus -- a South American freshwater catfish. Check the pictures here: http://www.planetcatfish.com/catelog/species.php?species_id=276 The usual "Shark Catfish" of the hobby is Sciades seemanni, an estuarine species.> I put them in my tank and fed them some bloodworms, about half a cube. Then when I came to look at the tank I noticed that both of them had large stomachs, it seemed like it was bulging out. Is this normal? <Sounds like they just ate a lot. So long as the bulge goes away in a couple of hours, don't worry about it.> I have read so many articles on bladder problems in fishes that I am getting worried in case something like that has happened to them. The lady in the LFS did say they eat bloodworms, so I that's why I fed it to them. What have I done wrong? <Likely nothing wrong.> Also, could you please tell me how to care for them properly, as I am not too sure if I have got my facts right. <Do read here: http://www.wetwebmedia.com/FWSubWebIndex/pimelodids.htm Basically easy to keep, but hyperactive and predatory, as well as fairly big, so bear that in mind.> I bought some bloodworms, tropical flakes (tetra) and some catfish pellets (tetra) and some other protein pellets as well which are JMC I think. In a plastic container, transparent with an orange top. <All sounds fine. They eat pretty much anything (including small tankmates!).> Thanks a lot for any help you could give me. Neervana. <Cheers, Neale.>

Re: Columbian Cat Shark  - 6/3/08 Thanks Neale, They look completely stunning in a Reef Aquarium, no one believes me when I tell then they are not actually real sharks and will not grow 6ft. The way they move and cruse the aquarium mid level and explore the caves makes them look remarkably like Reef Sharks. <Have seen them thus, and yes, the likeness is amazingly close, right down to the way they swim. One ichthyology text book I have begins the chapter on catfish by saying simply "Catfish do everything". Bold stuff from a scientist, but really very true. An amazing group of fish, and the more species you keep, the more impressed you become with their adaptability.> Theirs colours have changed from washed out silver to dark metallic steel grey, with a brownish dorsal fin, the rest of the fins are black with white tips. They have great appetites and are growing by the day. <Juveniles grow very rapidly. They level off around about 15-20 cm, and only very infrequently do aquarium specimens reach their maximum size in the wild of 35 cm. Some experienced aquarists have opined that there may be more than one species in the trade offered under the Colombian Shark Catfish moniker, and hence the variability in maximum size.> I have a very strong current in the tank from 4 power heads and they love the current. Not seen them sit on the tank bottom once... but then they even sleep on the wing...whoops...fin! Never stop! <Indeed so! They are migratory in the wild, moving up and down estuaries all the time.> Feeding them enough to maintain there activity level will be the challenge in a Reef tank without upsetting the water quality ! <Adults do need rather less food per unit body mass than the juveniles; it's generally recommended that big catfish be fed only every other day. I tend to prefer to simply offer small daily meals, ideally things that are high in fibre (like unshelled crustaceans) so that the fish feel full without too much protein (i.e., nitrogen) getting into the system.> Thanks again. <Cheers, Neale.>

Re: Shark Catfish 1/23/08 Hi Neale, <Neervana,> Thanks so much for your quick reply, was getting a bit panicky! So if they are swimming around really fast it doesn't matter? <Depends how you define "does it matter". Obviously these are active, river fish that need lots of space. In a small tank they will never do well, and will likely jump out or simply become nervous or sluggish. For Pimelodus pictus, the tank should be at least 1 m long from side to side, and should also have lots of water current, so the fish can enjoy swimming into the stream.> I forgot to mention that, they are going crazy, they are swimming REALLY fast and going crazy in the tank. <Typical for the species.> Do I need to add some stress zyme to calm them down a bit? <No. [a] That isn't what StressZyme does and [b] you can't calm them down -- they are river catfish and WANT to swim about.> Also if I have fed them bloodworms today, should I feel them those pellets tomorrow? <Always a good idea to rotate food items. You wouldn't eat the same thing every single day, would you? Mixing things up ensures the fish don't get bored and get a nice balance of nutrients.> Thanks, Neervana. <Cheers, Neale.>

Advice please. Re: Shark catfish, beh.  - 1/24/08 Hi Neale, (or if it's someone else) <It is indeed me.> I just wanted to say that my two shark catfish are doing very well now, they have calmed down a lot and are swimming peacefully but are trying to hide in a place where they can't be seen! The bulges in their stomachs have now disappeared (due to feeding them bloodworms yesterday) and I'm going to feed them tonight with a Tetra pellet each. I will take your advice on feeding them sparingly, with food each day other than big meals. <Cool.> When do you think I should do a water change? <Same as ever: once a week, 25-50%.> Because I just got them yesterday and I bought a tank for them so they could be alone, I don't know when I should change the water. I'm going to try and buy a vacuum gravel tomorrow with a water tester. The tank is fully cycled, but because they are new fish I don't know when I should start doing water changes. I know it should be once a week, but if I change it this Sunday is that too soon? They are very active and seem to be very healthy, breathing normally, have bright and have not lost any colour at all. They aren't stressed but sometimes they start swimming around crazily (which I take is normal from your previous answer to my email). <Don't worry about it. They're riverine fish, and swimming rapidly is what they do. Sometimes people turn the lights off just before doing water changes, so that the fish calm down a bit. Worth a shot I suppose, but since they're catfish I doubt they care whether the lights are on or not. Just don't chase the fish about with the hose pipe! Be gentle, and pour the new water in gently too.> Would appreciate it if you could advise me when to make the first water change. Is there anything else I should be doing? <Sounds like you have everything covered. Good luck!> Thanks, Neervana. <Cheers, Neale.>

Arius seemanni, strange behavior   4/2/07 Hello, I have two Arius seemanni in a 120-gallon tank. They are about 5 inches. Before they where very active, swimming constantly around using the whole aquarium. Now they stay in the bottom of the one end corner most of the time. Especially the leader seems sick (or not him/her self), swimming in small circles up and down, some times fast and some times slow, or just stay at the same place with its tail towards the ground and the head towards the glass and almost laying on the side. <Listlessness in shark catfish, Hexanematichthys seemanni, is not uncommon. The main problem is that these are migratory fish: they spend all but the first few months of their lives constantly swimming up and down estuaries between freshwater and the sea. They don't stay in any one set of conditions for very long. They are also intensely sociable, and when kept singly or in pairs tend to be far less settled than when in groups of three or more. Since they are totally non-aggressive towards their own species, it is even possible to add juveniles to a tank containing adults -- they will all happily swim together!> If I turn off the circulation pump and the light, this seems to help a little bit getting it to move a bit more around. They have no problems moving around when eating - I feed them more or less every day with bloodworms. <Provided they are eating, their health is probably sound, so I'd diagnose a psychological rather than a physiological problem here.> Some history: About one and half month ago I got problems with nitrite. It took me until a week ago to get the problem fixed. The strange behavior began about fourteen days ago. In the process of getting the nitrite right again, I slowly cut down salt to zero. When nitrite became all right again, I raised the salt in four days from 0 to 9 PPT (0.09 %). But the situation is still the same. <Why did you reduce the salinity when the nitrites went bad? Regardless of the situation, you need to adapt the filter to the salinity you want to keep the tank at. For shark catfish, around SG 1.010 is ideal, though they do well in seawater too.> By my reckoning, a salinity of 9 ppt is about SG 1.005, ~25% seawater -- far too low for long term care of shark catfish. When kept in low or zero salinity conditions, shark catfish seem to develop a very strong "migration" instinct, a desire to find different conditions closer to those that they'd inhabit in the wild.> Do you know what's wrong with them? <Likely the group is too small and the salinity too low.> Will they ever get back to normal? <As things stand now, no, probably not.> Can I do anything to help them? <Yes, buy at least one more catfish for the group, and then raise the SG to around 1.010.> Nitrite is all most zero, Nitrate is about 75, pH is about 8.3, total hardness is about 21 and carbonate hardness is about 8. <All fine for these catfish. They are very, very adaptable physiologically, but in terms of what conditions they "feel" happy in, they are picky. They are superb animals, in my opinion the most shark-like of all the "sharks" sold in the aquarium trade (except of course actual sharks!). But they aren't always the easiest fish to keep.> Best regards, Glenn <No problems. Neale> Columbian Shark help!!   3/14/07 Hi guys: <<Hey, Andy. Tom with you this time.>> I have some issues with Columbian Sharks I need assistance with.  I've had 2 of these guys in a 20gal freshwater tank for about 2 months (I bought them when they were juveniles).  I just transferred them over to a 55gal tank that I'm slowly transitioning into brackish water as I know these guys need it.   <<Andy, you must be one of the people that actually read. Very refreshing! :) >> However, ever since I put them in the 55gal tank, they literally just swim facing directly up in the front left corner of the tank.  They do this together (right next to each other) and RARELY leave this spot.   <<Acclimation here, Andy. New surroundings, etc. How tall is the 55-gallon as compared to the 20-gallon? You might not think it but deeper water affects some fish more than others. Most of these would fall into the 'labyrinth' category where getting to the surface is critical to their survival but 'low-runners' like your Columbians might be wondering what the heck is going on.>> I feed them bloodworms, flakes, krill, brine shrimp, etc. but they ignore all food it seems.  It is very strange because they were acting COMPLETELY normal with huge appetites in the 20gal tank before I moved them.  They also used to stay on the bottom, never the top corner like this.  Any idea what this is?   <<My guess would be that that they aren't at all 'fazed' by the additional swimming room, just the additional depth. Try dropping the water level in the tank. Give them the depth that they were accustomed to in the 20-gallon tank. Going to take some patience and calculating on your part where converting to brackish is involved but you can do it.>> I'm worried about them and want to prevent stress/illnesses in them so any advice would be appreciated!! <<These guys aren't 'deep-water' fish, per se, Andy. Of course, in the wild the depths are greater than in our aquariums but you need to think in terms of 'longitude' rather than 'latitude' in your tank. Look at how your fish are 'built'. They can adjust, with time, to a 'full' tank but you might be hurrying them along a little too soon. Lower the water level and see whether, or not, this gets them acting more normally.>> Thanks again, Andy <Mmm, are social animals... likely are "schooling" with their reflection. I would try temporarily (for a few weeks) taping a piece of newspaper or such over the pane they're stuck at. RMF>

Re: Columbian Shark help!! (follow-up question)  3/16/2007 <<Hi, again, Andy.>> Great idea, thank you for your assistance!  I did as you suggested last night and it already appears to be helping. They ate last night for the first time in 3 days!!   <<Glad to hear it, Andy.>> One more question for you.  In this tank (55gal in the process of being transferred to brackish), there are also 2 spotted puffers, 2 Dalmatian mollies, and one ropefish (Yes, they all get along!).   <<Still a good idea to keep a watchful eye here.>> The sharks, mollies, and puffers gobble EVERYTHING I put in there for food rather quickly.  I'm afraid the ropefish won't be able to get any food and will eventually starve as he doesn't seem to come out at all during feeding (I know he's nocturnal).  My question is this: Is there any foods that are specific to ropefish or anything I can put on the bottom that he'll find when he comes out at night? <<Unfortunately, Andy, the Columbians are going to be every bit as interested in whatever foods you select as your Ropefish would be so, it might be more a matter of 'when' than 'what'. Live foods are preferred by both but I would offer that you should stay away from small feeder fish of any description with your current stocking arrangement. (We almost universally advise against this anyway from a nutritional standpoint, however, it can/will 'trigger' predatory responses in both of these fish that the other fish, particularly the Mollies, don't need awakened.) You might try a food like sinking shrimp pellets later in the evening. These make it to the bottom rather quickly and might not get 'picked off' on the way down by the others. The Sharks, as you know, are scavengers but changing up feeding times may give the Ropefish a chance to feed while the others are less active.>> Thank you again for your assistance, I love this website and you guys are a HUGE help! Andy <<Thanks, Andy. We certainly appreciate that. If I may, while you've just recently 'upgraded' your tank, you'll need to keep in mind that your Columbians will need even more room down the road. These guys grow very large and the typical recommendation is about 50 gallons per fish. I suspect you are already aware of this but I like to point this out when the opportunity presents itself for our other readers. Keep up the good work and good luck with your new tank. Tom>> Arius seemanni dis./injury, beh.   8/1/06 Hey Guys,    I think your web site is great and I have learned a lot from you guys. Anyway I have a Arius seemanni he is about 6.5in and mostly just swims around the top of my tank. <Is a social species... should be kept in a small grouping> The other day he jumped out I was luckily there and put him back into the tank, he immediately started swimming like nothing happened. I did notice that his eyes where kind of foggy and he seemed to bump into stuff more often. <Likely "rubbed" its eyes... damaging them> But as of today 6/28 his eyes look good and I was told he had an infection.  What do you think? <I would do nothing in the way of chemical additions here... Likely will self-cure...> Also he is in full saltwater and all the water parameters are perfect.  He has no other catfish friends and I was wondering if he would be happy and school with coral catfish? <Mmm, no... Birds/catfishes of a feather/fin flock/school together... Better to have others of the same species... even if they start off considerably smaller in size> If so how many should I get? thank you for your and knowledge Joe <Bob Fenner>

Lonely Schooling Columbian Shark  7/28/06 Hey Guys, <Hi Joe, Pufferpunk here> I think your web site is great and I have learned a lot from you guys. <Glad to hear it!> Anyway I have a Arius seemanni he is about 6.5in and mostly just swims around the top of my tank. The other day he jumped out I was luckily there and put him back into the tank, he immediately started swimming like nothing happened. <I hope you add a nice, sturdy cover to that tank after that!> I did notice that his eyes where kind of foggy and he seemed to bump into stuff more often.  But as of today 6/28 his eyes look good and I was told he had an infection.  What do you think? <Whatever it was, seems to be gone now.> Also he is in full saltwater and all the water parameters are perfect.  He has no other catfish friends and I was wondering if he would be happy and school with coral catfish? If so how many should I get? <Since this is a schooling species, he would definitely like some friends like himself.  The fact that they can reach sizes of around 18" though, means a HUGE tank in their future, for a school of 5-6.  ~PP> Thank you for your and knowledge, Joe

Columbian Catfish & Brackish Water  6/25/06 Hello! <Hi Lou, Pufferpunk here> I have a few questions for you!  First--a little  history.  We set up a 10 gallon community tank for our 7 year old last  fall.  All was well--he does a great job testing the water and caring for  his fish.   <Good for him, at 7!  I bet he had a little help...> Anyway, Christmas Eve, my sister-in-law bought him two silver-tipped sharks and an algae eater. (Even after I told her that his  tank was at capacity and a PEACEFUL tank.)   <Bad, bad, bad idea to ever give pets as gifts!  I hope she was well scolded!> She gave them to him at 9 pm  Christmas Eve, so we had no choice but to put them in the 10 gallon tank.  They did very well but got fairly large.   <No surprise there--they can get to 18" if housed properly.> All three are at least 6 inches  long.   <Ummm... do you have 2 or 3?> We started to have water trouble and one of our zebra danios mysteriously, completely disappeared.   <Gulp!  Large water changes are in order for these fish, with voracious appetites & lots of waste in return.> We moved the sharks and algae eater into a 55 gallon 3 weeks ago.  (We do keep the water brackish for  them).   <The other fish you have will not appreciate any salt.  As far as "brackish" what do you mean?  Even for very low-end BW (a specific gravity of 1.005), it would require roughly around a cup of marine salt/5gallons.  At the size your Columbian sharks are now, they should be around mid-range BW, 1.010 (you'll need a hydrometer to measure SG).  They will require marine conditions as adults (at least 1.020).  They are also schooling fish.  So for a school of 18" fish, you're going to need a really HUGE tank!  (Time to go back to the sis-in-law for more scolding!)> My first questions are about the sharks.  They have always swam together.  Now that they're in the bigger tank, we can see them  better.  They swim almost vertical and push their whiskers out of the water near the filter.  Is this normal?   <Is there enough current or air-flow in there?  Check the water parameters (ammonia, nitrIte, nitrAte, pH)> They are very skittish and when startled, shoot back and forth across the tank at lightening speed.   <They might need more decor to feel safe.  Even some floating plastic plants might help (live plants don't do well in BW)> They  appear healthy and are growing like crazy but seeing their bellies constantly seems strange.  I thought they were bottom feeders?   <Generally anything with whiskers are.> Today they are actually swimming separate more, which is shocking and not constantly at the  top but still going up the sides.  Also, could they mate?  What would  we look for?  (Just baby sharks?) <Possibly but not in those conditions & tank size.  They will probably stunt in there.> We also have 3 tiger barbs and a gourami in the 55 gallon tank. <Opps!  Not BW fish.> The  barbs seem to nip each other and chase around in circles a lot.  Is this  normal?  Are they being "playful" or trying to harm each other?  It  seems like the same two going at it while the third darts in and out between  them. <Typical barb behaviour.> In a couple weeks, we were going to add another gourami.   <Not a BW fish.> Any other  suggestions?  We'd like a colorful tank but don't want to load up on any  more fish that will get so big!  What about a Bala? <Balas grow huge and again are not BW fish.  I think you should stick with these 2 (or 3?) & start saving for a larger tank & bags of salt.  They are fast-moving, active fish that may be disturbing to peaceful fish.  Do more research on BW fish.  ~PP> Thank you very much for your help!! Lou

Sharks <Arius cats> and a new tank 5/2/06 Hi, <Hello>   I have read quite a few posts but have not found an answer to my problem. Here it is. I bought 3 black fin shark <Arius...>, 3 platy and 1 pleco (from Wal-Mart, not sure what I was thinking). After reading the little description card I take these guys home, set up their tank and put them in it along with two live plants. That evening they were ok but the next evening one was swimming upside down at the top of the tank and seemed to be gasping for air. I immediately cleaned the tank which seemed to be very dirty and placed them in a holding bucket and pumped air in thru an air stone. It seemed very happy and normal again. I went out and bought a filter, a thermometer, heater, and an extra air tube. I already had the aquarium salt and air pump. Well I moved them to a 10 gal tank and setup all of the equipment. Good...everything back to normal..... Until today, again this shark, now swimming vertical and gasping for air at the top of the tank but not yet upside down. I don't get it because the other two are not acting this way. They like swimming in the air bubbles and lurk around the bottom of the tank. I am on my way to purchase a second air pump because for some reason I think this fish is short on air supply. So my question is what in the world is going on with this shark or is this normal?? I've only had them for 2 days now and am very uninformed and now confused. Oh and they are only about 2-3 inches long right now.  I appreciate any advice or info you can provide.      Jennifer <The short answer is that the tank needs to be cycled.  Please consider returning the fish and waiting until the tank is properly prepared for them.  The long answer can be found here http://www.wetwebmedia.com/FWSubWebIndex/fwset-up.htm , http://www.wetwebmedia.com/FWSubWebIndex/fwtips4beginners.htm and perhaps most importantly here http://www.wetwebmedia.com/FWSubWebIndex/fwestcycling.htm >.  Good luck and with a little preparation I'm sure you will be successful> <Chris> How to move big Colombian catfish  12/15/05 Hello. I appreciate all of the info on your web site and spend hours reading it. Here is my problem: One of my eight tanks is a 75 gallon brackish (SG about 1.013) with a trio of 8-9" Colombian catfish (Hexanematichthys seemanni); the oldest one is about two years old. They all look fat and healthy and, of course, just keep getting bigger. They're quite beautiful and impressive. <I'll bet... a gorgeous fish at this size> I haven't yet decided whether to move them to a bigger tank with better filtration and a skimmer (I planned to take them up to or near full marine) or to trade them in at a knowledgeable local store that sometimes handles brackish fish and has agreed to take them. Either way, I have to move these fish out of their current home. How should I go about catching such large, powerful, jumpy fish without injury to me or them? Every time I clean the tank I worry about getting speared, and they have a tendency to bang into the ends of the tank and scrape themselves on the filter intake tube when alarmed. Thanks in advance for any advice you can provide. --Brackish in Tampa <I would (carefully) drain the tank down, remove decor, heater... and scoop these fish out one or two at a time in doubled fish bags of good thickness (4 mil)... pouring some/enough water out to not tweak your back in the process. Do take care to "not get poked" by their spiny dorsal and pectoral fin rays (as you state...). Bob Fenner>

Silver-Tipped (Columbian) Shark  8-19-05 <Pufferpunk here> OK, another question.  My sharks seem to be happier in their bigger (55 gallon) tank, but they seem to favor one corner and they also swim up and down a lot, staying in the same spot.  Not at the top like they can't breathe, but closer to the bottom.  When someone walks over to the tank, they do as normal fish do and swim away.  Should I be concerned with this behavior?   Thanks, Kate <Sounds like perfectly normal behaviour for your fish.  Glad they have more room!  I hope you are planning to upgrade, as they outgrow the 55g.  ~PP>

-Columbian Shark Problems- Hello there, <Hi> I've recently tried adding Columbian Sharks to my 25 gallon tank with no luck. After a few days, they seem to change from black to grey. They look like they almost get a whitish coating and have trouble breathing.  <yes sounds like you tank water quality might be off. Check the Ph, ammonia, nitrites, and nitrates.> In the tank with them are a couple of guppies, some Tetras, a small white catfish, and two little frogs. Everyone else seem happy. My tank is about a year old. Any ideas as to what might be happening? What conditions do the sharks like best? Thank you for your help! Sylvia <Yes Columbian Sharks are a brackish water species that prefers a salinity of 1.005 to 1.008. If you choose to keep them, you need to keep them in a separate tank as the other fish are not brackish water fish. the reason the sharks are dying is because of the tank quality being off a bit probably and the sharks being brackish water fish. Good Luck. Justin (Jager)> 

Columbian shark Hi, my name is Chris, <Hello, my name is Bob> I have recently purchase a Columbian shark for my 65 gallon aquarium.  My question is that all day he swims the same pattern around the top of my tank, is this normal for him to do? <Yes, a very active catfish> My sg is 1.007, ph is 8.2, water temp is 79, nitrites, nitrates, and ammonia is 0, and phosphates is 1.0.  Other tank mates are: 5 African cichlids, 2 blood parrots, 1 scat, 1 Mono Argenteus and one tiger barb.  Any help would be appreciated.   <Help with? Your cichlids may not "like" the salt content indefinitely. Please read here: http://www.wetwebmedia.com/ariidcats.htm and the Related FAQs (linked above). Bob Fenner>

Iridescent sharks flipping out Hello, My name is Ted and I'm from NJ. This is the first time I'm submitting a question on this site though I've been on it many times. I think you guys are awesome and really appreciate all of your help and knowledge that you share. Thank you.  Ok, here's my problem.  I have two quite large iridescent sharks, one about 9" and the other about 12". I have recently moved them into a 72 gallon bowed front tank. Health wise they seem to be doing fine but they are getting spooked very easily. I've been leaving a couple of bags of gravel on top of the canopy because I'm afraid that I'm going to find one on the floor one day. <Good move> I have a feeling that being that its a bowed front that any outside objects or light might be making them flip out. <Possible> I never had a problem with them in their last tank. Though they were with other fish, and the tank was highly over stocked. (the two sharks, an Arowana, a parrot, a silver dollar, a Pleco, a clown loach, and a golden algae eater in a 90g) Obviously you can see why I moved them. I don't know, maybe its the tank, or maybe its the lack of aquatic friends. What do you make of it? <Mmm, the crowding and shape of this tank are problematical, but the worst trouble here is that these catfishes at this size are generally marine... Please read here: http://wetwebmedia.com/ariidcats.htm and the related FAQs linked above. Bob Fenner>



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