Columbian Cat Shark, comp., sys.   6/3/08
I have bought three Columbian Cat Sharks from my LFS. They were about 3 inches (2 weeks ago). I have put them in my 65 gal Reef Aquarium. Tanks mates are 2 common clowns and a six lined Wrasse which I think are going to be on the menu in a few months, but I have another marine aquarium they can be moved to.
<Interesting set up. The Shedd Aquarium in Chicago used to keep some species of Sea Catfish (I think Ariopsis felis) in a tank that was essentially a giant reef tank in the Rotunda. Sea Catfish look *a lot* like small sharks, and it was quite something to watch them cruise that tank.>
So far they seem fine with the soft corals and clean up crew, but when they get larger which is apparently going to be sooner rather than later given their current growth rate are they likely to eat the clean up crew as well, hermit crabs, turbo snails, emerald crab and common urchin?
<More than just "likely", it's probable! These catfish are completely opportunistic predators, and a significant amount of their diet consists of crustaceans of various times.>
The tank is furnished with macro algae, live rock, bubble tip anemone, devil finger coral, mushrooms, xiena and yellow star polyps (sorry about spelling?) These fish will be the priority in the tank and I wanted to create a aquarium matching there natural habitat so what should I used to create the biotype?
<Sea Catfish are estuary/inshore water animals. You find them in harbours, around rocky reefs (oysters beds for example), mangroves, sandy estuaries, and so on. So while they're not really picky animals, they have a preference for shallow water habitats where they stick close to the substrate. Their whiskers, electric sense, and (apparently) echolocation sense all help them to find food in turbid waters where other predatory fish would be at a disadvantage. In other words: classic catfish habitat! A perfect tank for them would have some big rocks (with sessile invertebrates if you wanted) and caves, an open sandy area, and a HECK of a strong water current. Not too much light if possible; or at least concentrate the light on the parts of the tank where the corals are, and leave some part of the tank shady. That said, they're wonderfully adaptable fish, and provided they have swimming space and a few friends of their own species, they aren't demanding. They mix well with most marine fish, though I've found they don't get along with Triggerfish -- triggers use clicking sounds as threats, so misunderstand the clicking noises Sea Catfish employ when communicating. The triggers attack the cats, the cats start clicking because they're frightened, and the trigger gets even more irate. As you can imagine, this isn't what you want, because both species are well armed and able to dish out serious damage. Triggers have whopping great bite, while Sea Catfish have an anti-coagulant bite (causes serious bleeding) plus venomous spines.>
Thanks
<You're welcome, Neale.>

Survival chances. Ariids and Balas? – 06/15/07
Hello!
<Hail and well met.>
I'm writing in regards to my 2 Colombian Sharks (about 2 inches long, maybe less). Well, the two that are left. (One died this morning.) I've done a lot of research lately and feel that these little guys are doomed.
<I hope not! Among my very favourite fishes. A bit worried about doing research on fish *after* buying them, but I'll let that pass for now.>
Currently, they live in a 55 gallon tank with 2 Bala shark.
<Wronger than a wrong thing on the wrongest day of the year. Bala sharks are freshwater fish, Colombian sharks brackish water fish. These two species cannot be kept together for any length of time.>
We're using the filter pump that came with aquarium. (It's a PetSmart aquarium kit). I don't think the filter is enough.
<Possible. A ball-park figure for fishes this size would be 5-6 times the volume of the tank in turnover per hour. Perhaps a bit more if you can, because Colombian Sharks especially love strong water current. In static water they tend to end up treading water close to the filter pump.>
We plan to add a under gravel filter.
<UG filters can be an excellent choice in brackish water tanks. Set one up as per a marine aquarium, with a filter plate, crushed coral, gravel tidy, and then coral sand on top. Use two powerheads, one at each end of the tank. This'll generate lots of water movement as well as keeping the pH high and the hardness level appropriate to the fish. On the downside, the Bala sharks will hate such water conditions, but they're going to hate the salt even more...>
After reading your FAQs, I learned that they are saltwater fish.
<Not really saltwater fish. Hexanematichthys seemanni is a true estuary dweller, and adults as well as juveniles swim up and down estuaries far into freshwater but rarely any distance out to see. So while they do very well in saltwater tanks, they certainly don't need saltwater conditions. 50% seawater, or SG 1.010 is fine. High pH and hardness, and especially lots of water current, seem to be more critical.>
I thought they were just brackish water fish.
<They are.>
I'm glad to know this because my husband disliked the idea of doing just a brackish water tank for these guys. Although, he really likes these fish.
<As does everyone who keeps them. They look like sharks, but don't get too big (30 cm is typical), and are as gentle as kittens (except to anything they can eat, of course).>
Here's my issue. I believe that I can not get anything bigger then a 55 gallon tank for them any time soon.
<That's fine for now. Growth is fairly rapid for the first year, when they'll get to about 20 cm, but after that, growth slows down quite a bit. But long term, yes, you may have a problem. Realistically though, rehoming these fish shouldn't be hard. Big adults are always in demand for additions to jumbo brackish tanks or fish-only marine aquaria.>
I live in a trailer home. I just don't think the floor with support a 100 gallon tank. It might support another 55 gallon tank at the other end. It may be half a year before I can afford another 55 gallon tank. Do these guys stand a chance of surviving that long with two Balas in a freshwater tank?
<Difficult to say. Their tolerance of freshwater is very high, and specimens 10 cm plus can survive in it quite well, assuming the pH and hardness are high. I've even seen fully grown adults in freshwater tanks. They weren't happy, but they were alive. I wouldn't recommend keeping them in freshwater though. For one thing, you'll find they become increasingly neurotic, seemingly looking for a way out so they can swim "downstream" to the estuary.>
If I do manage to get them into another 55 gallon tank and make it brackish water, how long do you think I can keep them in such living conditions?
<Forever. They do fine in seawater, but do just as well in very hard, pH 8.0 brackish water at SG 1.010.>
I plan to purchase a real house (eventually) and do a saltwater tank. This may take a few years and I have no idea if these guys will survive until then. If they do, will they get along with blue tangs and clown fish? (These are the kind of saltwater fish I /think/ I want)
<I've kept Colombian Sharks in saltwater tanks with things like Panther groupers and Domino damselfish without problems. Anything too big to be swallowed whole will be ignored by them. Pufferfish work very well. The only problems I had were with Triggerfish, which hated the clicking sound these catfish make (the trigger attacked the cats, the cats clicked in distress, and trigger attacked even more aggressively).>
What size tank would you recommend for a beginner in saltwater tanks? I know the bigger the better. I suspect that even 100 gallon tank might not be larger enough to start out with. I might as well find out now and start saving my pennies.
<Indeed, the bigger the better. I guess it depends what you want to do. For fish-only aquaria, a 55-100 gallon tank is a great idea because you can keep a nice selection of the large but colourful animals that wouldn't work in a reef tank, like Triggers, Puffers, Lionfish, Morays, etc. Definitely worth sitting down with a good book and having a read. Bob Fenner's "Conscientious Aquarist" is excellent, and I say that without him looking over my shoulder telling me too!><<Hey! I see this here/now! RMF>>
Thanks in advance for you advice.
<No probs.>
P.S.
I would consider talking my husband into returning these fish to Petsmart, but they have new rules. They have decided that you should not have more then one shark in a tank. If you do, they will not accept returns.
<Ah, a beautiful example of a Stupid Rule. For one thing, they're treating all fish with the word "shark" in its common name as being somehow similar. The problem with common names, and why experienced aquarists tend to dump them in favour of Latin names. What they mean to say is that people should only have one Labeo spp. or Epalzeorhynchus spp. "shark" (such as Rainbow and Red-tail Sharks) to each tank. That is indeed correct. But the Colombian Shark is not at all closely related to those fishes, and absolutely must be kept in a group. The bigger the group in fact, the better.>
We were told by a fish store that Bala Shark, Colombian Sharks and Rainbow sharks would do well together.
<Rainbow sharks definitely are aggressive and territorial. Bala Sharks and Rainbow sharks both need freshwater, Colombian Sharks brackish, so not really a viable combo.>
Now, my rainbow shark lives in a 10 gallon by himself for sending a Bala Shark into shock. (Which ended in death.)
<Oh dear.>
The Bala and Colombian sharks get along fairly well and even try to school with each other.
<How sweet! Both species need pals. Colombian sharks are rather adorable in this regard, and adults and juveniles school quite happily. People are sometimes worried about adding new catfish to the group, but no, they seem to really enjoy the company.>
I suspect the employees are the fish store are pretty knowledgeable, they just refuse to tell us the whole truth unless we ask the right questions.
<Perhaps. I can see where the Pet store is coming from, but in this case they've extended a serviceable idea way beyond its boundaries. Cheers, Neale.>

Arius seemanni Tankmates?  2/14/07
Hello,
<Hi Glenn, Pufferpunk here>
I have seemingly happy (8 cm) Arius Seemanni living in a 120 US gallon tank with (right now) a 16,5 PPT.
<HUH?>
My questions:
Is there room enough for more fish?
<Your catfish is a schooling species, so more of the same, would be my 1st choice.  A beautiful sight--a school of these fish!>
If so what about 3 or 4 Mono fish?
<Monos grow to a foot & would require around 300g for a school of them.>
If so Mono fish, which one would be the best in my situation Sebae or Argenteus?
<Neither, IMO.  Monos not only get large (as does your fish) but they are extremely skittish & your cat is quite the swimmer--not exactly a calming effect for a mono.>
If not Mono fish, do you have any suggestions (knowing that I want to go light marine).
<I'd say get a couple more Arius seemanni.>
What about Damselfish in light marine in company with 2 Arius Seemanni?
<You catfish will eventually eat them & anything else they can fit into their large mouth.  ~PP>
Thanks, Glenn

Salinity Woes 11/27/06
I recently bought 1 Pleco (3 inch), 3 Cory Cats (1inch), an Iridescent Shark (2 inch), and a Colombian Shark (2 inch) for my 55 gal. aquarium.  I know that the sharks will outgrow this tank.  <Yep>  My question deals with the salinity of the water, as I found out (after the fact) that the Colombian Shark will prefer a brackish/marine environment as it matures.  How much salinity will my other fish tolerate?  Thanks!
Kevin R.
<Not much/any for the Corys and Pleco.  This mix is not viable for the long term.>
<Chris>