Just a few days ago I added 8 Zebra Danios and 8 White Skirt Tetras to my 60 gallon tank of 8 Albino Corys.

One of the Danios is chasing all of the other Danios around. In fact it is bossy - but this only started today and the bloated Danio has been bloated since I got it. I thought it was a normal female trait. However the fish keeps floating up easily, but manages to stay down at the same level - leading me to conclude it might be swim bladder disease. Google turns up inconclusive. (Maybe it's pregnant?)

I've ruled out almost all disease, including dropsy, because it looks normal, just bloated.

I feed the tank freeze-dried brine shrimp and bloodworms, daphnia, sinking wafers, fish flakes, and that's all. The Danios 90% of the time eat what's on the surface, which is just blood worms and daphnia. Brine shrimp as well, but the tetras usually get that.

  • Where are you (locale) I am in Australia and I've noticed behavior changes, due to warmer weather and it appears to be mating behavior
    – user6796
    Dec 3, 2013 at 1:31
  • Is she actually unable to swim to the bottom?
    – user6796
    Dec 3, 2013 at 1:39
  • Not sure. They are able to swim around, this one is just waaaay less dense.
    – Don Larynx
    Dec 3, 2013 at 2:39
  • floating, I thought, was a sign of poor health and impeding death :/
    – user6796
    Dec 3, 2013 at 2:42
  • 2
    If the photos are crucial to answering the question, please include them, don't post them in chat.
    – Baarn
    Dec 3, 2013 at 10:20

3 Answers 3



Zebra Danios are extremely hardy fish. They are almost difficult to kill. They are indeed "bossy" and instill a rigid pecking order.


Definitely sounds like swim bladder disease. Swim bladder disease bloats the fish, and they struggle to retain the proper depth.


By the time you've identified a disease like dropsy or swim bladder, it's usually too late for the fish. The best treatment I've found is Melafix, but it's quite expensive, and very pungent and stinky. A single dose stunk up my entire bedroom and hallway for about a week, and the first few days I didn't want to come home because I didn't want to bear the smell.

To medicate the fish you'd optimally put it in a separate tank by itself, so your other fish don't get the treatment, too. But separating it often means a smaller tank, and the smaller the tank, the easier it is for things like pH to get out of whack.


Where did you buy the fish?

Department stores like Walmart are especially guilty of selling sick/diseased fish and not caring. Pet stores are generally a little better about it.

Did you know that you might be able to get a new fish replacement for free? Check your receipt. I like to hang onto my receipts for this reason, especially for expensive fish (which Zebra Danios aren't). In the past, I'd stick my dead fish in a baggie with some water into the freezer and take the frozen baggie with fish to the store for a free "exchange" with receipt.

  • Strangely enough, my Danios are alive. They are also bloated after eating. Maybe they eat a lot and get fat after eating? They have certainly grown. And no I do not buy from walmart...
    – Don Larynx
    Dec 18, 2013 at 19:38
  • I love the smell of Melafix! It's just diluted tea tree oil, good for various human skin conditions too.
    – calum_b
    Dec 19, 2013 at 14:44

My experience with Danios has that they always have been "bossy" fish. I don't recall one being the boss of the pack, but I recall that any Danio would usually go fin pecking the other species as well as their own species.

This wasn't due to overpopulation, a small tank nor under-feeding. It just seems that Danios have that kind of temperament and are territorial.

  • I know this doesn't answer the question about the bloated Danio, but I felt there was two questions in the post above: one on the bloat, one on the bossy attitude.
    – BlakBat
    Dec 18, 2013 at 11:38
  • It actually could be the answer. It could very well be that the one fish is bossy enough to hog all the food during feeding time. Generally it's catfish that will eat until they're about to explode. But I wouldn't put it past a danio to overeat simply to get all the food to itself.
    – Spidercat
    Dec 18, 2013 at 17:04
  • This is true. One of my danios hates it when the other danios get food.
    – Don Larynx
    Dec 18, 2013 at 19:37

Supposedly Danios need to school which mean you need at least 5-8 Danios in your tank. I had 3 , two female and one male. The male was very very bossy and chased the two female around endlessly. The two female got very fat. I was worried about the male Danio chasing them to death so got some advice that in order to make it stop you needed to add more of them to get them to stop being aggressive. I added two more which totalled 5 now. They just ended up zooming all over the tank and chasing each other. It was insane and stressing out my other fish. Then I tried to remove them all from my tank and it was impossible to catch them. After a few hours and after removing all my rocks, ornaments and plants, I could only catch 3. The other two are still in the tank being crazy and I took the 3 I caught back to the petstore. I won't get danios again as they are too crazy and stress me out.


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