Betta shredded fins and I don't know how
I have a single betta in a 5 gallon Fluval Spec V. This morning when I got up to go to school, his fins were fine and he was looking normal. I left for a few hours to go to school, and when I came back home his fins were all shredded up. All my plants are live (no plastic or even silk); I have an anubias, a java fern, an Amazon sword, some moneywort, and a marimo moss ball. Tank parameters are fine; when I checked yesterday before doing a partial water change ammonia, nitrite, and nitrate were all ~0. Temperature is ~78 degrees. I also have a baffle over the filter output to reduce the flow.
Any idea how this could have happened? He's been in this tank for about 3 months and this is the first time his fins have been shredded. It's worth noting that he likes to sleep against the filter grate, but the fact that he was fine this morning but damaged after he was already awake and swimming around for a few hours kind of makes me think that's not it. I've included before and after pictures, as well as a shot of the tank.
Before (His fin is split but had since mostly healed; this was when I had a plastic plant in the tank)
After
Posted Mar 6, 2018, 8:48 PM UTC
If it definitely wasn't the filter, the only thing I can think is he snagged himself either on that decor or on a rough spot on the rock. Something might have startled him, or he just went for a quick turn and got himself caught on an edge somewhere.
Is it something I should worry about or should I just keep a close eye on him and watch for if it progresses or happens again? I don't see any particularly sharp edges on the decoration or the rock, but I also haven't sanded either of them specifically to make them smooth so it is a possibility.
You could do what we call the panty hose test. Take the decor and the rock out, slide a pantyhose across them. If it snags anywhere, sand down the sharp bits until that's not a problem.
If he's been in there months without issue then maybe its a non-issue? As long as the water is clean and he's otherwise healthy, they should heal up eventually.