Thank you, but I am still not sure if I would be able to identify it in time because it still looks so similar to torn fins.Most judging is done by how the damage looks and how fast it's progressing.
Fin nipping will usually result in a large amount of damage in a short amount of time, and the damage usually starts out looking like u shaped pieces missing out of the fins. If the fish is dedicated, like one of mine was, he can trim off nearly half his tail in only a few days.
Damage from decorations mainly causes rips in the fins. Sometimes the rip will be long, other times it can cause the ends of the fins to look frayed, BUT fin nipping can also cause the fins to look frayed. Again a good bit of damage can occur in a short amount of time.
Fin rot usually causes the fins to look like they are slowly disintegrating. It sorta looks like the paper does when it's lit at the bottom and the flame is allowed to burn up the paper. It generally develops slowly and the fish will often act sick. My yellow veiltail developed a mild case of it after I forgot to plug his heater back in after a water change. His tail looked like it had melted a bit and it had a red edge to it, but what first caught my attention was his lethargy. Fin rot usually progresses slowly but there are some varieties of it that can move quickly.
This thread, https://www.bettafish.com/99-betta-fish-diseases-emergencies/346377-lets-talk-fin-rot-vs-fin-biting.html , has great pictures that will help you see the difference.
It really does not.Thank you, but I am still not sure if I would be able to identify it in time because it still looks so similar to torn fins.
So what I should really be looking at is the fish's behavior?Fin Rot is extremely rare. It happens, mostly but not always, in tanks with poor maintenance. Read the sticky in the Diseases and Emergencies section on diseases triggered by poor maintenance. Unless sickly when purchased, few fish become sick in tanks that receive regular weekly 25%-50% water changes.
You will truly know if you see it...just don't depend on Google photos.
@Rainbo describes it well. But one other thing that will differentiate Fin Rot from biting is the Betta with Fin Rot is sick and the fin biter is not. So the fish with Fin Rot will reflect the sickness in body posture. They will not flare, they are listless and often do not eat. Their fins look "fused" (called "melting").
A fin biter, on the other hand, will still flare, eat and zip around the tank as if it had not a care in the world.
Examples of body language of Betta with Fin Rot. Note, especially, the Blue Betta and his fused caudal fin.
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