V. Some Fish That You May Not Want part 1:

Colombian Shark Catfish

There are more than a few fish that show up in stores which realistically cannot be maintained in captivity in the home short of unlimited budgets and considerable professional assistance. Too many of these are just too big to be managed as a hobby fish, but stores may tell you that they can live in hobby tanks. That is unjustified. If you keep a horse in a dog crate, does it become a house pet? I suspect that you know the answer to that question. The same thinking applies to fish. This is the first of a projected series of articles on fish that are only marginally appropriate to inappropriate for hobby home fish keeping.

Sciades seemanni, a.k.a. Colombian/Columbian Shark, Silver Tipped Shark, White Tipped Shark, Black Fin Shark, Jordan’s Catfish, and probably other names as well. Fishbase* gives the “common” name as the Tete Sea Catfish – which I have never seen or heard in the hobby, but may well be the common name used by taxonomists. These are apparently always sold from freshwater (FW) in the fish stores, but even at the smallest sizes seen should be in at least hard alkaline water. They are caught from estuaries or from rivers near the sea and are in fact brackish water (BW) as fry to marine or saltwater (SW) as adults, with feeding forays into estuaries and up tidal rivers throughout their lives. Fishbase lists their maximum size as 35cm. SL (standard length between 13 and 14 inches) but larger captive fish have been reported from both home and public aquaria. They are schooling fish and should be kept in groups of at least three and preferably more of their own kind. Solitary specimens tend to be very easy spooked and may injure themselves against tank walls and/or equipment. They should have marine mix added to their tank as soon as possible; bringing the specific gravity gradually up to ~1.005 over a few weeks, but it is best done gradually, not in a single step. At this low salt level there should be no issues with the biofiltration bacteria. By six months to a year in captivity they water should likely be at least double that density with a specific gravity of at least 1.010. During their second year they should reach maturity and be adjusted up to marine conditions during that time, but still with gradual specific gravity changes, best at no more than 0.002 per week change in specific gravity. Somewhere in the range from 1.008 to 1.012 specific gravity the nitrification bacteria will start switching over to SW forms. If any ammonia or nitrite appears in the water, the changes in density should stop until those un-oxidized metabolites disappear (become undetectable by hobby test kits). Then very slowly start increasing density again, with care and testing. At full strength marine conditions (1.o21 – 1.025) the bacterial biofilter may be gradually replaced with more effective SW techniques including live rock and foam fractionation / protein skimming. Those functions may be housed in a sump as desired.

These fish are opportunistic predators. That means that if they can eat another fish or invert, they will. Due to their size and the need for keeping at least 3 as an absolute minimum school, even in a 180 US gallon tank there is not sufficient room unless a substantial sump, perhaps a 120 US gallon, is added to the display. Three 14 inch active swimming fish is not a small bioload to realistically support long-term. Other tank mates are pretty much beyond the carrying capacity of the set up. Operating costs will be higher until the setup is on the more efficient SW techniques.

Feeding is routine while the fish are small, standard aquarium fare is generally accepted well. By the size of six inches, gradually introduce fish market fare (frozen and thawed but not cooked) to reduce costs. People food is far cheaper than fish food.

Fish from this family, the Ariidae, have rather sensitive hearing and do not handle loud or sudden noises well at all in captivity. They may frighten from such and injure themselves or leap from the tank. Perhaps the commonest cause of death in captives is secondary to injuries cause by inadequately sized tanks and injury to the fish following a fright. Loud or percussive music is risky.

This family shares another common characteristic – the first spine of their dorsal fins is venomous. Be extremely careful when you must have your hands in the tank. No sudden moves or noises, please. The pain or risk may be your own.

Do you think a several thousand dollar investment for 10-15 years – plus SW maintenance costs during that time – is really worth it for these fish? I do not. The choice is yours.

*Fishase is an on-line taxonomic reference site, and the scientific names they list are those that I use in all my articles. The site does provide some information which can be useful to hobbyists beyond that of which scientific name is currently in fashion. The web address is: www.fishbase.org

Robert T. Ricketts, Jr. a.k.a. RTR

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Robert T. Ricketts

Retired research scientist (biochemistry and physiology, pharmaceutical development) and senior process analyst. Started fishkeeping in the dark ages (1950s), first SW tanks in the mid-60s, first puffers in the early 60s. Started with two tanks and never less than multi-tanked excepting some periods in college and grad school. Specialty if any would be filtration and water management. Primarily species tanks, planted whenever possible/practical and some where it not really practical. Ran something on the order of >150 tank-years* in studying optimum tank conditions for F-8 puffers, the largest tank study I have done. Other studies have been significantly less. Alternate canister use was mid-40s, OERFUG just over 60, veggie filters only about 25 to publication, but still going on less intently. If it had been known that the F-8s would live so long, it probably would not have been started at all. *One tank-year is one tank for one year.