bent fish

Question
i have a 30 gallon tank which i change the water every 1.5 to 2 weeks water temp is between 76-78 i change about 3 gallons at a time i have 1 filter on it.. i dont know what kind of filter is it is the one that came with the tank..

the problem i have is i got up this morning and my clown knife is bent in the shape of a u.. there are 3 fish in the tank a 3 in loch and a 3.5 in plecostomus. the knife fish is about 6 in long i just did a water change yesterday.  i never have any problems with my water when i test it.. the ammonia was 0 the nitrate was 10 and the nitrite was good also but i do not remember


Answer
Hi Joe
Let me give you a few suggestions first.  Up your water changes to once a week, and change out about 25% of the water and being sure to vacuum the gravel/substrate well.
Clown knife fish grow extremely large, about 2-4 feet, so plan on a serious tank upgrade in the future :)  Here's a link with some basic info on them:

http://www.badmanstropicalfish.com/profiles/profile5.html

Sorry, not sure if you were aware of that, but I have to mention it due to how large they do grow.

Now for the fish bent in a U shape.  There are several possible causes of that.  My first guess would be a vitamin deficiency.  Not sure what the fish eats, I know it's common for them to eat feeders.  Feeders generally aren't the best diet for fish, they really don't have much of a nutritional value.  If that's all he's eating, it might be a good idea to try to vary his diet a bit more so he gets different vitamins.  I don't know if this is possible, since a lot of fish that eat feeders don't want to eat anything else.  Just have to be persistent and maybe even having to fast him for a few days till he accepts the other foods.  Try to vary it up with some frozen foods like brine shrimp, blood worms, regular earthworms, squid, shrimp, even different types of frozen fish.  Make sure to thaw all those out before feeding.  You could also soak the foods in a liquid vitamin(like Centrum) for a bit before feeding.  Same would go if he's eating pellets or flake food, vary it up.  Another thing, if he is eating feeders, consider breeding your own.  Feeders from the store tend to not be kept in the best of conditions, and it's a good way to spread diseases and parasites into your tank.  

A second possibility, there's 2 diseases that can cause a fish to have a bent spine.  Fish TB, not the same as the human form of TB, but it CAN be transmitted to humans.  And neon tetra disease.  I'm enclosing a link with additional symptoms of those diseases to look out for.  Both diseases are listed on the page. I don't know how prone CK fish are to those diseases, but it is possible-especially if you're using feeders from a fish store:

http://www.fishdeals.com/fish_diseases/stressdisease.shtml

If you suspect it is one of those, be sure to thoroughly wash your arms and hands after messing with the tank=good idea to do anyway.

Another possibility is there's electric current going through the tank.  This can happen through a faulty heater or even the filter.  

Hope that helps and good luck!

Christy