Topic: I was doing my weekly 100 percent water change and I had him in the container he came in while the water aged with water conditioner. Later on I noticed his fins, not his body, had lost color. What should I do? Is this more of a fin related issue or the entire fish body issue? What should I do in my case…
Reply from BettaGeek:
I do not recommend doing 100% water changes on any fish tank. To accomplish a full 100% of new water you would have to remove the fish from the tank itself right..? That’s not good to be moving around your fish in different tanks. But maybe your exaggerating on the 100% and you really just do 90% water change and leave your Betta at the bottom in a little bit of water while you get new water.. this is still bad. I would only do a 50% water change at maximum in any size bowl or tank. A lot of people preach this “full 100% water change” and I think that’s crazy unhealthy for the fish.
Make sure you don’t have too powerful of an aquarium filter that would give too much surface movement for your fish. Bettas need to go to the surface a lot and if they are getting stressed out by that surface movement.. they may get sick.
But aside from that, now we need to asses your color loss issue. This may have been brought on by the drastic water changes for the fish. What happens is, the fish gets used to the water it is in and starts to adjust to it. Then when you completely remove all the water and add totally new water… it puts the fish in shock again of trying to get used to the new water. Their organs and such become under stress. Fish are very susceptible to dying from stress.
It is very comparable to humans breathing air. What if I stuck you in a room where the air was totally different.. your lungs would struggle to keep up and it would be a painful transformation.
Get some Epsom salt from your local convenience store. Add one teaspoon for every gallon of water in your tank. The salt helps with digestion issues since these are the most common issue with Betta fish. Do your 50% water changes quite frequent like maybe once every 2-3 days. If your tank has gravel on the bottom.. get rid of it if possible. Gravel is home to lots I bacteria that would blow your mind. Most of the bacterias are good for your tank but some are bad. I’m doubting this is the issue but that will help bring down the circumstances that are making your fish sick.
Start starving your Betta fish. Yes you heard me right! Digestive issues are a huge problem for these fish and your fish could have just ate too much. This issue HAPPENS ALL THE TIME. The common saying is “give your Betta a pea to cure it”. You can try that as well. Starve your fish for 3 days and then give the fish a “half feeding” and go from there.
It kind of sucks when our bettas get sick because it can’t just be one variable or aspect when fish get sick. They can’t speak to us so we must try to cover all ground of what is wrong with their situation. Hopefully that helps with your issue and I apologize about being so blunt. It’s just my personality so don’t take anything to heart 
Maybe some other people will have some to add too. Because you know… I don’t know everything about Betta fish ????