Expert: Susan Fields - 9/17/2006

Question
Dear Karen,
I have had three iridescent sharks in my aquarium for the last 6 years.  They have been treated multiple times for ulcers on their bodies which have always gone away.  Recentley one of them developed ulcers which when treated went away..yet the fish has become skinnier and more ill looking.  He is in very bad shape and has gone from floating at the top of the tank to now just laying on the bottom.  I have correctly used the ulcer medication and done a 40% water change and now have no clue what else to do to save my fish.
                    Can you help me save my fish,
                                Mike

Answer
Dear Mike,
I'm sorry to hear about your Iridescent shark! Bacterial Ulcerations have several causes, whether it be enviromental (poor water quality) or other factors like stress of any sort. I would imagine since you've had your sharks for 6 years now, they have probably put on some good size by now. Iridescents frequently grow well over 12" inches and frequently grow three feet or more. And that many sharks would certainly put out quite a bioload. It's very important to determine the underlying cause of these Ulcers rather than simply treating the symptoms. I would definately check water quality and insure your ammonia, nitrite, and nitrate are all in check. As a rule, ammonia and nitrite should always be-0  and nitrate- 20 or less. You should also take into consideration anything that could be stressing your Sharks like overcrowding, other fish (bullying), too small a tank, and anything else you might suspect to be stressing them.

Remember too that the ulcer medication likely has been destroying your beneficial bacterial colonies which are so important to sustain since they keep ammonia and nitrite levels in check. It could even be that your fish are suffering from ammonia and nitrite from constant bacteria die-off due to the medication use.

I would try to test your water as soon as possible for ammonia, nitrite and nitrate. And above all.*I would begin daily 50-60% water changes until you see improvement. Remember to always treat the replacement water with a proper water conditioner and insure it is equal in temperature to that of your tank everytime.

Unfortunately, it may be too far gone for your ill Shark. I really don't like to say it one bit but all the sickness and medications and possibly even poor water quality could be weakening him greatly. I'm very sorry. That's a very sad deal you have there.

Feel free to write me from time to time about how well your Iridescent sharks are doing. I am more than happy to help you all I can!

Best wishes,
Karen~