Columbia sharks dying help!!!

[stasey]

I have a 33G tank that I have had set up for about a month now (cycled)added 6 glow light tetras at first then 3 columbia sharks and later 2 angel fish all was good for a while no amnonia spikes all water levels good. The other day I did a water change and I do not think that I had enough water conditioner to get all the chlorine out of the tap water I noticed that my water has a haze to it and there is like a white chalky film on my filter and on the glass and now I am down to one shark the others are dying or dead the other fish all seem ok does anyone know if the white stuff could be chlorine ? or does anyone have any suggestions ( Should I take my other fish out of that tank and put them in my bigger tank till I get this figured out???)

 

[Sorrell]

Columbian Sharks get to be 14 inches and are 100% marine at maturity. I don't know how young yours are, but they may be suffering from lack of salt. Personally I would return them to your store and stick with a fish that is freshwater and who's size is compatible with your tank

Here's some info on them

Columbian Sharks

 

[stasey]

we have some in another tank that have already grown to about 7 in . So I am not thinking that that is the problem I do know that they need salt at some point but they are only babys now about 2 in long . I have had the other four for 6 months or so . They will go in a bigger tank as they grow we are getting a 100 g soon

 

[Sorrell]

Since that link doesn't go straight to the page, I'll copy and paste


Scientific Name Hexanematichthys seemanni Günther, 1864
Common Name Colombian Shark Catfish, Shark Catfish, White Tip Shark Catfish
Type Locality Central America
Pronunciation sea MAN aye
Species Information
Size
350mm (14") SL

Notes on ID ID based on adult specimens, the young fish appear regularly in the hobby and various species (from coastal Peru and Brazil) may be available. The differences between many of the genus are slight at an early age.
Sexing Immature at under 300mm length, female has lighter fins in adult fish.
Habitat Information
Distribution Pacific rivers from Southern California down to Colombia.
Temperature
22 - 26°C

pH
6.8 - 8

Other Water Parameters Salt should be added in relation to the age of the fish. The older the fish, the more salt, right up to 100% marine. The fish is very tolerate of changes of salinity and will live in freshwater happily as a young fish.
"Furniture" Large, open spaces not too brightly lit, this fish is an active shoaler although initially youngsters are quite shy if not given plenty of plant cover. Rocks and or wood are unnecessary.
Husbandry
Feeding A true omnivore, these fish are often near starvation when bought at the smaller than 2" size but can be brought on very successfully on frozen bloodworm. Once acclimatized, feed less protein rich foods such as catfish tablets. The fish can be trained to approach the surface to feed. Adults can be fed frozen prawns intermittently.
Compatibility Very similar to South American Pimelodids, keep with fish that like similar water conditions and are big enough to prevent being considered prey. Youngsters (smaller than 12cm) can be kept in alkaline fresh water (with for example rift lake cichlids), but larger fish MUST have salt added to the water in order to thrive.
Suggested
Tankmates Initially most medium sized active fish, but with the addition of salt to the water as the fish grow, brackish water fish such as Monos, Scats or large Mollies are the order of the day.