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FAQs on the Zebra Danios Behavior

Related Articles: Barbs, Danios & RasborasA Barbed Response; Wrongly maligned for being fin-nippers, barbs are in fact some of the best fish for the home aquarium by Neale Monks

Related FAQs:  Zebra Danios 1, Zebra Danios 2, & FAQs on: Zebra Danios Identification, Zebra Danios Compatibility, Zebra Danios Selection, Zebra Danios Systems, Zebra Danios Feeding, Zebra Danios Health, Zebra Danios Reproduction, & Barbs, Danios, Rasboras 1, Barbs, Danios, Rasboras 2, B,D,R Identification, B,D,R Behavior, B,D,R Compatibility, B,D,R Selection, B,D,R Systems, B,D,R Feeding, B,D,R Disease,


Zebra Danio Ducks For Cover   7/23/09
Hello, I am in real trouble here!!!!!!!!!!!!!!!!!!!!!!!!! I was putting in a new filter cartridge and my female zebra Danio just went bizerk!! She swam really fast then sat down under a plant!! I am VERY worried she will die soon what should i do??? Pease hurry back!!
<Usually small fish like to be in small groups or schools They are easily spooked in groups less than six. I am sure after things calm down you will see your Danio out swimming around.-Chuck>

Baby Danio Released 11/21/08
Dear WWM Crew,
Hi, I just released in my 10 gallon tank a female baby Danio that I raised from the beginning. The baby Danio is a little bigger than an inch.
In the beginning, she was just swimming around with the four other Danios with no problem. I just noticed now that she is swimming close to the top.
<I'm a little confused by the title... did you recently move this Danio to a new tank with other Danios? If so, she might just be adjusting to the new environment.>
Could it be because she is not used to the current?
<If all the other fish are healthy and there's nothing wrong with your water quality, I would just assume that she is just "getting oriented." I wouldn't worry yet.>
Should I remove her or give her time?
<Nah... just keep an eye on her.>
The other Danios every once in a while follow her around at the top of the tank. Please give advise. Thanks for your help ahead of time. Jean
<Careful observation is about the best I can advice for you at this time... wait and see what happens. Maybe she just hasn't been "officially" admitted into the school yet... ;-)
Sara M.>

Development of a Danio Fry  9/5/08 Dear WWM Crew, Can you please tell me how long it takes for a Danio fry to develop (weeks/months)? Thanks for your help in advance. Jean <Hi Jean. It should take about 3-4 months for the fry to develop into fish big enough (half adult size) to either return to the aquarium or sell on. They are sexually mature within 6 months; males generally a lot sooner than that. Growth is fastest during the first few weeks, but this depends on them getting lots of meals (ideally, as many as 6 per day) and large scale water changes so that nitrate in the water is minimised. Water temperature also makes a huge difference. Cheers, Neale.>

Zebra Danio, olde... beh.  07/14/08 Hello, <Ave,> I have a zebra Danio who is 5+ years old. <Quite an age for such a fish! Well done.> I have one other zebra Danio who is less than a year old, there was another younger zebra Danio but he died a while ago. <Oh.> Once one of the younger zebra Danios died the other young one began playing with the older one. <Hmm... "playing" isn't something most fish do. So, the question is whether the fish are merely swimming about or actually chasing one another aggressively. Danios are schooling fish and need to be kept in groups of 6 or more specimens. If the group is too small, specimens will chase one another, sometimes to the point that weaker fish are stressed, even killed.> Then the older one began hiding under this ship thing in the tank. <Ah, not this isn't a good sign. The one in the open is likely "dominant", and the one hiding is unable to come into the open because it gets chased.> I don't know if that is relevant at all but I thought I'd just say it anyway. <Very relevant. I suspect the key problem here is stress, brought on by social behaviour issues. Make sure you have at least 6 Zebra Danios and all should be well.> This was all a few months ago. Now the older Zebra Danio has come out of the ship and just floats on his side all day long. <Not good.> If another fish swims by it and touches it or something he will start swimming around again--just as fast as the younger one. <Mmm...> Also, during feeding time he usually starts swimming around and eating. <All consistent with stress.> All of the other fish seem perfectly healthy. <Are the other fish Zebra Danios or other types of fish?> I am not sure if he is just old or is sick. <May well be too old to put up with the energetic youngster. Go buy six more Zebra Danios and then there should be enough members of the school that the one "bully" can't throw his weight around too much.> Any ideas? <Yep.> Thank you, <Most welcome.> Megan <Cheers, Neale.>

Re: Zebra Danio 07/14/08 Hello, <Hello again,> Yeah, I figured that might be the problem. The other fish are mostly platy's because they had babies which are now about full grown. I gave away some of them because my tank is only 15 gallons but I don't have enough room for anymore fish without it being too crowded. <Indeed.> I will try to find a home for some of the platys. <Aquarium shops usually take these, and may even give credit.> And once I do I will be sure to get some more Zebra Danios. <Ah, sounds like a plan.> Thank you so much, Megan <You're welcome, Neale.>

High pH, Fighting Danios Hi guys. You have the greatest website! I got my first tank two weeks ago. It is a ten gallon freshwater community tank, several plastic plants, 50 watts heater, two thermometers one internal and one external, one fake rock with 3 holes on it, one undergravel filter, two inch deep gravel strata (rounded and more or less pea sized), one aqua-tech outside power filter, one small sponge filter. The pH of our tap water is about 7.4 to 7.6. I added water conditioner (Tetra Aqua Safe), Stress Zyme, five teaspoons of salt for freshwater aquarium. At the beginning the water got a little cloudy. I waited one week and added 3 Zebra Danios Next day I added one ounce of Bio-Spira freshwater bacteria from Marineland. The water became clear again within 24 hours. The Danios (one small male, one small female and a larger older individual whose gender is a mystery to me) were fine. They were exploring and racing around. Then the two smaller Danios began to dance in circles at the bottom of the aquarium. The older individual took possession of the upper and middle part of the aquarium and began to chase and bump-fight the small male while the small female was hidden in the plants. Within 48 hours the small male stopped racing and eating and died. I examined the body. There were no signs of disease or injury. The older individual still chases the small female every time they meet. The small female is fine but she is confined to a corner of the aquarium that is covered in plants most of the time. She ventures out often, but she goes back when the larger Danio chases her. When I feed the fish, I feed them very little food, twice or once a day. I try to feed them the minimum amount of food possible. I underfeed them because they are too busy fighting each other to eat all of it. Although the Danios come immediately to the food, they promptly begging to fight and some flakes end up sinking and the fish remain hungry. I worry about the food sinking. My last pH reading is in the range of 7.6 to 8. My ammonia reading is 0. My nitrite reading is 0.2. I have several questions: What could have happened to the small male Zebra Danio? <<Aggression, high ammonia, nitrites. What did your ammonia test at last week? Must have been some, there has to be ammonia for it to be converted into nitrite. Do you have nitrates yet? You should be testing this tank everyday.>> What is it with the large Zebra Danio (I was told they are peaceful fish)? <<They are not. And a toxic tank will not make them any nicer, either...>> Could the small female Zebra Danio be hurt by constant harassment? <<Certainly>> Is it a good idea to add other fish to the tank? <<No.>> If so is this list a good list: one male Beta, two more Zebra Danios, two female Guppies and two small Cory Cats? Are this fish too many (taking into account all my filters and that I am willing to do a 25% water change weekly and a mayor water change monthly)? Would they take my pH as it is? How can I modify this list to avoid disaster? <<Do NOT add any fish now. Your tank is still cycling. Hence the high pH, etc. And certainly don't add all of these at one time! And definitely avoid putting guppies and a Betta into a tank with Danios. Disaster awaits if you do.>> Until now I have resisted the impulse of applying pH-lowering product to my tank but What can I do with my pH (7.6 to 8.0)? Should I make a 25% water change now (taking into account that the food keeps sinking because of the fighting of my Danios)? <<As I said, your pH is high because the tank is CYCLING. It will stabilize in a month or so. Have PATIENCE, please. Do not mess with your pH, you will not be helping your fish if you do. The pH will end up all over the place, and your fish will end up dead from a combination of pH shock, nitrite poisoning, and stress..>> Finally, If Bio-Spira is so amazing, why are some dealers against it? Thank you for your help. <<I personally like Bio-Spira, it's an excellent product when it's being used properly. However, results will differ from tank to tank. Dealers simply don't like it when people with no experience try to cycle with it and end up with dead fish, as in your case. Please do some reading, buy yourself some ammonia, nitrite, and nitrate test kits, and be PATIENT. Test your water regularly, do water changes when readings become high, and do NOT add fish until the tank has NO ammonia and NO nitrites left. Keep two small fish in the tank during cycling. TWO! not more! Keeping a written record of your test results will help. :) -Gwen>>

Danio Swimming into HOB Filter - 3/16/2006 Hey Crew, here is a new one...to me, anyways. I have three zebra Danios in a 10 gallon cycled quarantine tank. I am seeing some very odd behaviour from one (or perhaps two) of these fishes. Twice in the past 24 hrs, one of the Danios has found his way up into my hang-on-the-back power filter. I say "one" of them, but I am not sure...it could have been two different fish who did this. On both occasions, I have found the fish swimming around in the confines of the filter's media chamber, unharmed. Does this behaviour signify anything, other than the antics of hyperactive fish? <<It is likely out of curiosity, but could be a sign of something else.  How are your water parameters? It could be due to aggression from the other fish as well.  Keep an eye on them, just in case.>> Is there any device I can employ to stop them swimming up into the filter? <<If there is no screen in the intake, try some filter floss, or a bit of screening of some kind to fashion your own.>> It is rather alarming to me that they are doing this, not to mention risky to the fish when I have to retrieve them. <<Risky in general.  Do cover the intake!>> Any help you can offer is appreciated. <<Glad to help. Lisa>> JM

Minnow behaviour & health    10/3/06 Hi <Hello there Charlotte> I have four pairs of minnows (2 zebra Danios, 2 coldwater, 2 long fin and 2 yellow ones: apologies for the lack of description by proper name but I can't remember). <Perhaps a small journal you can keep...>   They all get along quite happily with four fancy goldfish and a coldwater Plec and all seem in general good health, having joined the goldfish approx 6 months' ago. On Sunday, I purchased 3 very tiny fantails (one smaller than the zebra minnows!) and all seem well.  Today I have noticed that the yellow and long-fin minnows seem to be displaying to each other by opening their fins wide and synchronized swimming! I have been trawling the internet and my books but none give any indication as to what this behaviour means. <Perhaps reproductive behavior... maybe just dominance displays> Is it possible that it's due to the slightly reduced territory now there are 3 new fantails (albeit very small ones) or is it a breeding thing (one of the yellow ones looks a bit portly)? <How large is this system?> As a secondary point, on reading various articles relating to minnows I noticed in one of yours reference is made to a bent spine indicating TB infection. <One possible cause of several... covered on WWM.> This concerns me as one minnow has a very bent spine.  He's always looked like this, has grown well since purchase, as have all the other fish.  As mentioned above, all of the fish in the tank seem in general good health and water quality is fine.  Should I be concerned about TB or do I just have a minnow with a wonky back? Your comments would be greatly appreciated. Many thanks, Charlotte <Please read here: http://www.wetwebmedia.com/FWSubWebIndex/gldfshsystems.htm You may need more room, less fish livestock. Bob Fenner>

Zebra Danio acting strangely 5/6/08 Hello, <Sarah> I have an established hexagon tank, I believe it is 35 gallons. I had e-mailed last Sept when some of my fish died suddenly after a heater malfunction. Since that time, I have not added any other fish, we had 1 zebra Danio and 2 Cory cat. This weekend I picked up 5 very small zebra Danios at Petsmart (where the other fish came from as well) and 2 more Cory cats. I have checked the water daily, it still shows zero nitrites. All the new fish seem to be active and happy. The coloration on the new Danios brightened from a pale brown to bright stripes almost immediately. All the Cory cats are happy. However, the one original Danio is acting strangely. It seems to be swimming in a labored fashion, moving his tail constantly, as if it cannot keep itself straight in the water. Its tail is lower, and its head is high. He has had a bloated look for a very long time, so not sure if it could have some sort of problem. Any suggestions? I had wanted to get more Danios so he would have someone to school with, as he was just hiding in the plastic plants all the time. Now he's out and swimming, but not looking good. Also, he has a large bright red spot on one side behind the eye- is this normal coloration for zebra Danios? Thanks, Sarah <Mmm, is not... could be most anything at this juncture, description. Please do send along a well-resolved image if you can. Bob Fenner>

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