columbian sharks

mollies

I have a 3 inch columbian shark that stays in a 6 inch area of my tank. It is a 55 gallon. I had 2 of them that did realy good for a month then just died over night. Then i got this one a week ago. He eats fine. All of my ph amon nit nitrates are all good. Why would he be doing this? Why would they die like that no ick or any of that in the tank?

iamntbatman

Well, Colombian sharks are not a freshwater fish. They need brackish conditions and even full marine as adults. The young are born in fresh (or almost fresh) water but you need to slowly increase the salinity as they grow. If the salinity is too low, it weakens the immune system of the fish and can make it much more prone to diseases. Also, keep in mind that Colombian sharks grow very large (two feet or so) so you'll need a much larger tank. I'd say a six foot tank minimum, although eight would be better.

If you want a similar looking fish with similar behavior that would work in a 55g tank, Pictus Catfish would be a much better choice.

mollies

Iv got the colum shark. This one is doing good now I think he just needed to get use to the tank. An i tryed the pictus cats. They didnt seem to last but a day in my brakish tank. The tank is a brakish i have mollies, archer, colum shark in the tank. I have a 125 gallon that they will go into when they get a little bigger. I realy like the colum sharks. Thanks for the help.

iamntbatman

Ah ok. The thread wasn't posted in the brackish section so I assumed it was a freshwater tank. With brackish water fish acclimation is especially important. "Brackish" can mean anything from very slightly brackish to nearly full marine conditions, so it's always a good idea to get a salinity measurement from the store where you're purchasing the fish and try to match those conditions at home. If you already have an established brackish tank that is significantly more or less salty than the tanks at the store, you should consider setting up a quarantine tank* with the same salinity as the store's tank. That way, you can introduce the fish without the risk of osmotic shock, keep it quarantined to watch out for disease, and slowly adjust the salt level in the quarantine tank to match your own brackish display tank. Then, you can transfer the fish to your display without problems.

It could also be that many fish stores don't really treat their brackish fish right. Even though you're keeping them in brackish water, the tank at the store could very well have been fresh (as it's cheaper) and thus moving the fish straight from fresh to brackish could have been a big shock. Doing so could have weakened the fish's immune system enough that it could have gotten sick and died after a month.

I'd say a 125g is a good minimum size for Colombian sharks. Beware that it likely will eat your mollies once it gets some good size on it.

*Actually, quarantine tanks are a really good idea in any case, it's just that they're especially useful when dealing with brackish water fish for the reason I already mentioned.

mollies

Thank you for the help. OK i do have the 10 gallon quarantine tank set as the salinity as my lfs. My tank is just a bit more then the stores. That was my problem. again thanks