black ghost in trouble

Question
Dear christy i have a 2 feet  tank which houses 2 silver dollar a few tetras and a black ghost that is about 17 cm long. from the past 2 days i have been seeing it rub itself against various surfaces in the tank kike fake plants and stones apparently trying to relieve itself of itch or sumthing but let me tell you he doesn't seem to have ich coz there are no white spots on him. i have not done my regular ( once a week) water change could that be the reasonhe is eating and all with a good apetite but his behaviour is worrying me plz help me.

Answer
Hi Sai
Fish that scratch or rub on objects in the tank could be suffering from a parasite infection-and just because you don't see the white ich spots doesn't mean it's not ich.  Just may not be showing up yet.  But, it could also be from water quality, and especially if the ph is changing, which can happen when water changes aren't done.  So, what I would suggest is doing a water change as soon as possible.  If he continues to scratch and rub after that, then I would go ahead and start a treatment for parasites.  All your fish in the tank are sensitive to salt and a lot of parasite meds, so you need to be careful with what you choose.  You could go with the salt and heat method, but just keep an eye on the fish for signs of stress, and add the salt slowly over a few hours.  Dissolve it first in a bucket of water.  Or if you can find a medicine that says it's safe for scaleless fish and tetras you could try that.  Here's some links I have on ich and different treatment options:

http://www.aquahobby.com/articles/e_ich2.php

http://www.peteducation.com/article.cfm?cls=16&cat=1791&articleid=2421

http://en.wikipedia.org/wiki/Ichthyophthirius

Good luck and hopefully the water change will take care of the problem, and let me know if you have more questions.

Christy