Question: how to cure open-gill in bettas

> i have a male betta with one gill open, do you know how to cure this and why it happens.

This is considered a defect in bettas in our book. Most of the time your bettas will live a normal life, that open-gill wont bother them at all. Spawning-wise, if the open-gill is on one side, then it's ok too. They learn to spawn from the good side ;)

We believe there are 2 reasons why bettas get this problem:

1. genetics
   
2. environment

If your bettas have genetics abnormalities, then there is no way for you to cure it. It's there and inherited. Usually your fry will have a perfect gill when hatched till about 1 month old. Then you started to notice one or both of their gills to open up wide for a much lengthy period of time. Before you know it, you're too late, the gill got stuck and stays open forever. This category theoretically is not really "genetics" since it will only happen at about 1 month old. The gills are used to pass air bubble (if you watch your fry for some time, you'll notice how the air bubbles come out of the gill). Some bettas have weak gill muscles where the air bubble got stuck in the gill, forcing it to open for a much longer period of time. Long exposure of the gill seems to cause the muscle to tear and that injury shows up as your open-gill problem... Many people attributed this to simply bad water condition ;)

The second cause of open-gill problem is caused environmentally. For instance, we regularly use rough fishnet to scoop bettas. What we noticed in small and big bettas, if the gill got stuck on the fishnet and the bettas do not recover from the injury, they will end up with open-gill problem too. You can avoid the problem by changing the fishnet to a cloth-based one, for instance. On rare occasions we see adult bettas develop this problem by flaring for too long period of time. The gill is no more than a constructed muscles, tear happens...

Now, as for the cure, there is no real cure for it. Knowing the cause of the problems usually help you to devise a cure. For instance, we have cured a couple of adults that starting to develop open-gill problem by giving them a good rest after flaring exercises. This has to be done as early as possible, when you notice they're developing it ;)