Berta's tail damaged?

Betta's tail damaged?

I'm a new fish owner who just got a Betta fish last Saturday. My tank was cycled and at the right levels, my tank is a mixture of real and silk plants (Java moss and Java ferns), a Top Fin 10 Gallon Filter, and the one Betta. Everything was fine until yesterday when I saw a part of his tail was missing, and he was acting fairly aggressive, flaring his gills and darting around. There were faint long strands straggling at the ends -- it looked like damage from the filter suction.

I panicked and got some Bettafix, did a half dosage, and I replaced my filter with a modified Penguin 100, a small sponge at the output to ease the water flow. I looked at him today and the strands are gone. I didn't see him flare today, but he was still darting. There is no discoloration on the fins, either today or yesterday.

Should I be more worried? Is this fin rot or was he just injured? I've barely had him for a week, and I want to do anything I can to keep him healthy.

Edit: I have searched on this forum and others for what's going on, but all I found were posts on fin rot.

 

I honestly have no idea, so I'll call in some people who are very experienced with bettas. Flowingfins BornThisWayBettas

 

First, I would take the bettafix out ASAP, it contains melaleuca oil. This oil irritates the labyrinth organ causing it to expand which will suffocate you fish.
Are there any rough decorations in there that he could tear his fins on? Do the plastic plants have any spiky parts?
I would do a 50% water change every two days to heal it, medications won't be necessary.

 

There are some grass stems that are made of plastic. I'll cut them off and do a water change when I get home from work tonight. His tail looked a bit shorter this morning, but I couldn't get a clear view. I hope he'll start healing soon.

Thank you so much!

 

Quick update: I noticed the intake was too strong for him, and for some reason Crash likes to swim near it. I cleaned a fish net with some freshly conditioned water and tied it around the filter intake.

I got rid of one of the larger silk plants. The edges were frayed and there was a lot of plastic. I did a water change yesterday, and will do one tomorrow. His tail has largely remained the same, but I'm hopeful he'll make it.

Thank you for your help!