Question about Black-finned/silver-tipped/Columbian sharks

Hi all, first time visitor. My fiance and I have a trio of these beautiful fish, and one has developed a "twitch" recently. All of the other fish in the tank are fine, and he is 90% of the time, but once in a while, he'll be swimming, and just twitch. Best way I can describe it, is imagine a fish on dry land flopping, and that's what he does, but while he's swimming, and only once at a time, not like a continuous seizure or anything. we haven't changed food or anyhing recently, although we did upgrade him to a bigger tank about a week before this was noticed. I'm just curious as to whether this is somethign to be concerned. Also, we did take a sample of the water to a fish store, and they tested the water, pronouncing it just wonderful for those guys. Any help would be greatly appreciated in setting the fiance's mind at ease.

 

Does it look like he's itching himself on decorations?

How big is the tank and what other fish are in it? How big are all the fish?

What are your readings for ammonia, nitrIte, and nitrAte? (actual numbers, please - pet store employees generally know squat about fish even though they pretend they're experts)

Are you adding any salt to the tank?

You should be aware that columbian sharks are NOT freshwater. They tollerate freshwater when they're young, but as they get older, they need more & more salt until they're in almost a full saltwater environment. He very well could be reacting to not having enough salt. But depending on what your other fish are, they most likely will not tollerate too much salt. Which means you might have some incompatable fish on your hands.

-Chelle

 

I dont have chemical readings handy, i'll try to take some tonight and post them tomorrow. No, no itching, just a funky dance-twitch. it's a 20 gallon tank. all of the fish in it are these 3 (all under 4" as of right now), a spotted raphael cat, a red-tail black shark, and a rubber-lipped plecostamus. feed them a combination/mix of flakes, blood-worms, algae tablets, and catfish (bottom-feeder) pellets. we are adding some salt to the tank, but not in large amounts. Where we got the fish in question, they informed us of the brackish nature of them, but also said that it wouldn't be "required" until he got a bit older, so i was expecting at least a few months before having to worry about that. :?

Thanks for the quick reply and help, by the way!

 

It is possible for it to be in regard to the salt content. It sounds more like PH shock to me. Fish can go into PH shock up to two weeks after they have been aclimated. You could add a PH buffer like Novaqua, but after being in there a week adding the buffer is probably not going to make any difference other than aiding with slime coat production.