healthy betta fading fast

Question
regarding my bizzare and puzzling issue with my siamese fighter. lately i've noticed that his colour is fading from his dorsal fin down on either sides of his body. there is no fuzzy growth associated with the faded area. on the colour fading front the scales have a dark granular accumulation around their border. i have kept an eye on the fading and it has definitely spread and is now even starting near the tail!

what's puzzling is that he's not old (i've had him for ~7-8months) and he seems to be eating, moving and behaving normally. I feed him twice a day 2 pellets of Betta gold each time. once a week i take some of the stones that have algal growth out for a wash and top up the water, but generally i do a 1/2 water change with Betta basics once a fortnight as they do not mess up their water much. lately i've been using a bit of algae clear as there is a bit of algal growth but i make sure i stick to the dosage rate. the tank is kept out of direct sunlight, but is kept in a well lit area. the temperature is maintained pretty consistantly at ~20-25degrees.

the fish is kept in a tank with another fighter in an adjoining compartment and the other fish does not seem to be affected. last time this same fish got a slight white spot outbreak, the other fish was again unaffected.

should i be worried?


Answer
Hi Sheung-Yi;

It may be a disease known as Columnaris. It is caused by bacteria. That particular fish probably just happens to be weaker in general so he gets sick and the other doesn't. It happens with other animals and even people. Here is more info about it;

http://www.mushi.petfish.net/columnaris.html

If the tank kas no filtration they do need a 100% water change every week. 50% every two weeks is not enough to keep them healthy. If there is a filter, change 25% every week. It is harder on the fish to wait so long between changes. The water chemistry is altered enough by that time that it can shock them when it finally is changed. Making more frequent changes could definately help the sick one's immunity.

I hope he feels better soon....

At Your Service;
Chris Robbins