Im Stumped

Question
Chris here is the deal, I have a 75 gallon tank that has been set up for a year.I have one nine inch silver arowana that i've had for about 6 months. I bought the fish in good health atabout six inches long, there is a piece of driftwood in the tank (plastic)and that is it. I have a magnum 350 deluxe canister filter with 2 biowheels. I feed it twice a day with frozen beefheart from the push out package. My ph is 6.7, ammonia and nitrite levels are no trace. In the last 2 months the fish has gotten something resembling fin rot but the edges of the fins are black. I have tried many medications such as melafix, myracin, and many others, some people told me to raise the temp and add salt then do water changes,but nothing works, and the arowana is still steadily deteriorating. He shows no strange behavior, still eats steadily, just totally normal other than this disease. I had a silver arowana about 4 years ago and he was no problem took care of him the same way. Food twice a day and a 25% water change every 2 weeks. My old fish was even in a smaller tank. Everything I have tried has failed and i hate to give up these fish are so great. Please help any input would be appreciated. Thanks Kory,

Answer
Hi Kory;

Black edges on fins usually indicate ammonia burns. The ammonia is down now but it can spike and sometimes we don't even know it unless it causes the burns or the fish act stressed. It happens sometimes. Ammonia can spike for two or three days and then go back down again as the bio-system compensates. The burns can take a few weeks to heal and the fins may look pretty bad as the dead tissue sloughs or "falls off". As long as he acts fine now and you don't have any ammonia in there anymore he should heal just fine. Keep the water very clean so there is a lower chance of infection. If the edges start to look white or bloody, it indicates fungus or bacteria has infected the injured areas. You can add aquarium salt and MelaFix to help him heal and help inhibit infection. They are both available at fish stores.

Ammonia spikes are from the biological balance being disrupted or overloaded. This can be caused by several things; New Tank Syndrome (obviously not yours), over cleaning of the filter, addition of new fish, overstocking and overfeeding. Beneficial bacteria colonies in the filter and in the gravel, as well as on aquarium surfaces, usually consume all the ammonia and nitrites. If we clean out the filter and/or replace media in it sometimes too much of the bacteria is killed or disrupted. If there is too much food or too many fish are added at one time, or just too many fish are in the tank in general, the ammonia will go up as the system tries to grow more beneficial bacteria colonies to compensate. If any of those factors were possible a few days before the fish began to show black fins, the beneficial bacteria colonies may have been disturbed too much. It sounds like whatever caused it has passed and hopefully it won't occur again.

Do you have other fish in the tank? He may be getting picked on too. Sometimes fish that seem to get along well for quite some time will grow bigger than you think before you know it, start maturing and begin to become more territorial. They can start trying to breed and get pretty aggressive too.

Let me know how it's going...

At Your Service;
Chris Robbins