A “blow-out” is a term betta breeders and hobbyists use to describe a small hole or tear in the fin tissue caused by spreading or “flaring” of the fins. Torn or frayed fins can be caused by a number of things including bacterial fin rot, injury from tank décor, biting from other fish or even from a betta nipping his own fins. The term blow-out is not used when holes or tearing are the result of anything other than tension in the tissue caused by flaring.

Since these tears are caused by flaring, only the unpaired fins (dorsal, caudal and anal fins) are typically affected. Bettas most at risk for blow-outs are those bred to have very large fins or excessive amounts of fin tissue, such as halfmoon bettas or rosetail bettas. Bettas with smaller fins or those who don’t flare as much are less likely. Female bettas don’t typically get blow-outs, nor do plakats (short-finned bettas), however, it should be mentioned that any betta could get a blow-out; some are just simply more at risk than others.

While blown-out fins are usually blamed on excessive flaring there are other likely factors that contribute to the tearing including genetics (large fins with thin tissue) and water parameters. Bettas predisposed to bacterial fin rot may have more blow-outs due to the degradation of fin tissue. Again, poor water quality is not the sole cause of fin rot, but merely a contributing factor in some cases.
The most common type of fin-blow out is a “pin-hole”. This is a tiny puncture that occurs where the tissue is stretched the thinnest. They are very commonly seen in the dorsal and anal fins. Pin-holes are very minor tears and usually require no special treatment. They typically heal naturally within a couple of days.

Holes larger than a pin hole can be treated simply with clean water. For severe blow-outs, API’s antiseptic BettaFix has proven to be very effective in reducing the healing time. Follow the manufacturer’s dosing recommendations carefully. If you are noticing frequent blow-outs or thinning of the fin tissue and suspect that it may be the precursor to bacterial fin rot, begin by testing your water parameters and increasing your water changes. If fin rot does develop treat with an appropriate antibiotic rather than BettaFix.

Blown-out fins are common and are generally considered a cosmetic problem rather than a serious health risk. Most heal themselves in just a few days. If you are worried that your betta is flaring too much and his flaring is causing his blow-outs, check out our Tips for Hiding Your Betta’s Reflection.

Beautiful Healthy Betta Fins

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Reader Interactions


  1. Lilie says:

    My fishies fins have white coloring on the tips, is that normal? And I’m noticing right now that (already fed) he’s eating from the pebbles from the bottom of the tank, is he supposed to do that?

    • Christie F. says:

      It’s hard to say what is normal in terms of betta coloring. They come in nearly every color of the rainbow and often the color is not solid. To complicate things, their color changes over time. Is white coloring at the tips normal for YOUR betta? Did the color appear overnight or does it look as though it is fuzzy or diseased in some way?
      As for feeding off the pebbles, yes, this is normal. Healthy bettas should be active; frequently exploring their tank and nibbling from various places.

  2. Lilie says:

    Also, he’s a crown tail, how can I find out that he has good fins?

  3. Catherine says:

    thank you for this article. My betta, Beloved, is experiencing this. I couldn’t understand why .. I had the water tested and it was fine. The woman at Petco said that I was keeping my water too clean. She did have me treat for fin rot with lifeguard for I was also getting a milky slime in the tank as well. It’s been almost 2 weeks since I treated his tank. This has helped with the slime, but his top fin is sticky and I noticed this morning that he now has a blow out hole in it. I started this morning adding bettafix … good to know I did the right thing. As for reflection I have a tank that has angles 5 altogether and I do believe this could be an issue – I don’t think I can correct it very well. Any suggestions … I don’t want to buy another tank

  4. Caity says:

    Just wondering, but the fish pictured with the healthy fins – what is the name for his specific colouring? Is he green, turquoise, or multicoloured? My crown tail looks identical to that, and I couldn’t figure it out earlier today. Thanks 🙂

  5. betta luv says:

    i herd that you can give your betta excersize by putting a mirror out side of the tank and let him flare at his reflection could that cause fin blow outs?

  6. Cari says:

    I have had my betta for about 6 months and never had any issues with him. However, this evening I noticed the center of his top fin is a whitish clear color and there’s a tiny hole in it. He was completely fine last night when I fed him dinner. He is in a 3 gallon tank alone with 2 soft artificial plants. I’m pretty concerned and clueless on what I should do. Anyone have any suggestions?

  7. Helen says:

    I have a white pearl halfmoon (I think) betta, who developed a tiny hole in his caudal fin a few days ago. This tiny hole enlarged over the next 48 hours to be the size of a pencil eraser, and finally his tail split cleanly to the edge. He shows no symptoms of any disease, there are no other signs of ailment on his body or fins. He eats well and swims vigorously. The water is very clean (2 gallon nano tank with filter), the plants are live and soft (dwarf grasses), and the gravel is designed for dwarf shrimp (also very soft). Have you heard of spontaneous fin splitting before? (I have photos, if you’d like, just let me know.)
    Thanks in advance!

  8. Alycia Queretaro says:

    I just recently got my mom a half moon betta and i have noticed that his tail is literally falling apart at the base. Could he be blowing his tail. Also how long will it take to grow back?
    I do clean his bowl out out every couple days and i put aquarium salt in his bowl as well.
    I have bettas my self and treat the water the same on all of them and havnt had this happen before.
    So any information on what is going on would be appreciated.

  9. Olivia says:

    I think my halfmoon betta recently had a tail blow out. At first I just assumed it was fin rot, so I treated him with aquarium salt for 7 days, and he seemed to be doing a bit better, and he wasn’t flaring because I covered the tank with pajama pants to keep the heat in. I put him back in his normal tank today, and now he is flaring like crazy because he has two female betta friends in the tank next to his which he can see. His tail doesn’t seem to have gotten any better. He is also extremely active. Is there anything to do other than wait?

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