Columbian Black Finned Shark...

I have a Columbian black finned shark in a fresh water tank. The tank is a well filtered 20 gallon tank, with water being changed often. The other fish in the tank are a common pleco (soon to be moved), 2 cory catfish, a male swordtail, and a tiny angel fish.

The shark was added four days ago. He seemed quite fine. He was a very shiny silver. The shark tended to swim against the glass.

Today, however, he is not doing as well. Maybe he has just mellowed down a bit after the change of enviroment, but it is noticably paler.

I have read that the Columbian shark is a brackish water fish, but in a number of places have read that when small they do fine in freshwater. Should I move it to a brackish water tank ASAP or give it more time in the fresh water and let it adjust to the new enviroment?

Yea, we are aware that it needs a bigger tank. It is looking much better today. Hopefully it will be fine until we progress to a larger tank.

liv2padl said:

that depends on how long it takes for you to "progress". if your fish is 3 inches right now, you've got about 4 months at the outside before you begin to do permanent damage.

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It was kind of forced upon us, so we are doing the best we can for it.