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FAQs on the Zebra Danios Reproduction

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 Behavior, Zebra Danios Compatibility, Zebra Danios Selection, Zebra Danios Systems, Zebra Danios Feeding, Zebra Danios Health, & 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,

Hi Crew; regarding Danios potentially spawning.   4/26/10
Hi Crew,
<Hello Erin,>
I'm an amateur fish hobbyist and at the moment I have 8 Longfin, yellow and zebra Danios in a long 20gal tank. I've had them for over a year, and have had no problems apart from one fish that died due to a bent spine, and being the 'weakest' fish in the tank. At the moment, 4 of the fish are absolutely huge.
<Does happen with Danios, for a variety of reasons. They eat like pigs to be sure, but the females will fill with eggs quite readily too. More worryingly, like many minnows, they're prone to Dropsy and other such complaints if kept under less than perfect conditions.>
At first I thought they were heavy with eggs, but I noticed that one of the fat fish has some scales along its back that stick up.
<The famous "pine cone" appearance is a classic sign of Dropsy, which is, as you seem to realise, a symptom rather than a disease. Dropsy is difficult to treat, so the main things are to [a] avoid it and [b] if it does arise, optimise water conditions and hope for a natural recovery.
Antibiotics may help, but the problem with small fish is that by the time you see the symptoms, the internal organs have been damaged already, likely beyond repair. Bob favours Furan medications and Chloramphenicol. Do read
Its a very active, assertive fish, one of the largest and healthiest of my specimens, so I didn't immediately think something was wrong,
<If he's still swimming and feeding, that's promising, and antibiotic medicated food would be the best approach here.>
I actually thought it had something to do with their spawning.
<Females can swell up, so sexing your Danios will be part of the process.
Also stop feeding; if the fish shrinks down across a few days, maybe a week, then you're laughing. Do also think about the fibre content of their diet; Danios naturally consume much indigestible material in their diet, such as insect exoskeletons, and an all-flake diet could easily cause constipation. Follow the same basic ideas as for treating those big minnows we call Goldfish, and they should fix constipation in these little minnows we call Danios.
Now I'm worried that there is some bacterial issue, as the dominant male doesn't seem to be taking any more interest than normal in the females. Is this ridgy back a strong suggestion of a bacterial infection?
<Can be.>
If so, what should I treat them with? I already set up another tank, thinking that they were going to spawn, should I isolate the fish with the ridges, or all the fat fish?
Regards, Erin.
<Dropsy isn't contagious as such, any more than a stroke or heart attack in humans. Like those things, it's a symptom of an underlying problem, not a disease in itself. But when one fish does show signs of Dropsy, you do need to determine why. Common long-term stress factors likely include monotonous/nutritionally inadequate diet; water with a high nitrate/low oxygen content; overstocking; and quite possibly genetic predisposition as well. Cheers, Neale.>

Re: Hi Crew; regarding Danios potentially spawning. 4/26/10
Hi crew.
<Hello Erin,>
I'm beginning to think this fish might not make it, I came home and checked on him/her, and it is only really swimming in the top half of the tank, and doesn't really look pleased with life. So sad for a fish that was so healthy
to have gone downhill this fast, I wish I'd spotted something wrong sooner.
I have only been giving them very small feeds for the past two days (I have been conditioning them for spawning) and this one hasn't gone down in size at all.
I think I may need a new water testing kit because all my results have been coming back as 0-0.1... I do a partial water change every 4 days or so, so I'm not sure how Dropsy could be affecting them unless I'm feeding them the
wrong foods.
<Small but non-zero levels of nitrite and ammonia might not seem serious, but they do indicate problems with stocking, filtration, overfeeding. So you do need to bear that in mind.>
I feed them TetraMin small pellets for tropical fish (this is in Australia so I dont know if you will be familiar with the brand) but I have been recommended Okami? Not sure of the spelling.
<TetraMin is a great food, but it's always a good idea to mix things up. The easiest way is simply to raid the kitchen! Cooked/tinned peas are good, as are small bits of fish fillet and seafood, even tiny bits of hard boiled
egg yolk. Herbivorous fish will gladly go for courgettes, carrots and all sorts of other things, even cooked rice. So this isn't something to get too stressed over.>
Perhaps this diet change will help, as I think I'm doing everything right when it comes to water quality. Ill get a new tester kit and change their food and hope he pulls through. Is there anything else I should/could try?
<See previous e-mail and the pages you were directed to.>
I'm not sure how much an antibiotic/medical treatment will cost, and my funds are sadly a bit limited.
<Do be aware of basic methods of euthanasia then, as here:
Also, their tankmate is a 3.5 inch algae eater (when I bought him 6 months ago he was barely 2 inches)... has he reached his growth limit and can no longer keep up with eating the algae and keeping the tank clean?
<"Algae-eaters" don't keep tanks clean. That's advertising, not reality.>
Am I overstocking the tank with 8 x 2inch Danios and a 3.5 inch algae eater?
<Depends on the "algae eater". Are we talking about a Bristlenose Plec, Ancistrus sp.? That gets to about 12 cm and along with a school of Danios would fill out a 20 gallon aquarium.>
I get such conflicting information online about how many fish will fit in a tank, and have tried to err on the side of caution.
<Wise. There's really no hard and fast rule. If you think about the "inch per gallon" rule, 120 Neons and 1 Great White Shark have the same number of inches, and you want to guess which needs more gallons? So there's some art as well as science here. If the fish are healthy, you're fine; if they're getting sick, then you may well be overstocked.>
Regards, Erin.
<Cheers, Neale.>
Re: Hi Crew; regarding Danios potentially spawning. 4/26/10
Hi Neale,
First of all thanks for the very speedy replies. As you can tell I was quite concerned, thinking maybe this was a highly contagious issue, so I'm glad you were able to reply so rapidly. My particular tester kit will either come up with a 0 (90% of the time) or very rarely with a 0-0.1 result, and I always do a water change and test again the next day if this occurs. I didn't know about being able to feed them peas, so thanks for the tip :)
The algae eater is a Chinese algae eater
<A useless, bad fish. Gyrinocheilus aymonieri. Gets to 35 cm/14 inches, and above about half grown, it becomes notoriously aggressive.>
and, from all that I've seen, does seem to feed off of the walls and gravel, so I assumed he was industriously doing what I was told he would do (aka, contributing to the cleanliness of the 'house' like a good tankmate should).
<Gyrinocheilus aymonieri is an algae-eating species when young, but as it matures it switches to a more mixed diet. Really a fish with no value, and sold only to people who don't do their research...>
If worst comes to worst, I will have to euthanise the little fellow (sob), so thanks for the link to that part of the site. Ill inquire about the medication at the Aquarium store on Wednesday, but I have a feeling it might be too little, too late by then, so euthanasia might be the kindest option.
Its a shame, too, because I was just about to transfer them all over to a 30 gal, perhaps if Id had time to do so sooner, whatever is causing this issue might have been resolved.
Thanks for all your help and if you're interested Ill let you know if the little fellow recovers. I'm so disappointed, I was really hoping they would spawn. Back to the drawing board, it seems.
<So it seems.>
Thanks again, Erin.
<Cheers, Neale.>

Zebra Danio breeding     3/21/10
(RMF, you may have some comments to make here)<<Nothing more to add>>
Hi, I had a question about breeding Glo Fish (Zebra Danios) .
<Illegal to do so. Wherever you bought them should have told you that you have the legal right to own, but not breed, Glofish. In buying these fish, you accepted the licensing agreement, which you can read again here:
So strictly in terms of keeping Wet Web Media away from the tender mercies of the lawyers at Glofish, we can't give you any explicit information about breeding Glofish. With that said, these are merely genetically modified
Danio rerio, and what holds for breeding Danio rerio holds for Glofish.>
I'm not going to sell them, because I know you need a permit to do so,
<No, you misunderstand the license you agreed to. You cannot intentionally breed OR sell them; it isn't JUST selling that's against the terms of the license.>
but I wanted to breed them anyways.
<In which case you are breaking the terms of the license. This is just one reason why I'm glad genetically modified animals like Glofish are not traded here in England. There are 30,000 fish species out there, and I'm more than happy to breed some of those. I don't see the need for scientists to create new fish that lawyers won't allow me to breed if I want to. Half the fun of keeping fish is breeding them!>
I don't have them in a conditioning tank yet, I still have them in my main 100 gallon tank but conditioning them there to tell which are males and which are females.
<With Danio spp. generally, it isn't easy. Males tend to be more boisterous, and females -- when ripe with eggs -- are noticeably plumper.
But other than these traits, it is very difficult to sex them.>
They all are getting fatter, including my other fish in the tank, but ALL of them are getting fatter.
<Make sure you aren't overfeeding them!>
I have 7 of them and was sure that I was bound to get at least 1 male when I got them.
<Assuming equal numbers of males and females in any given batch of fish, yes, choosing at least 6 specimens should almost ensure you get both sexes.
But for a variety of reasons such as water chemistry parameters and differential growth rates, fish don't always produce equal numbers of both sexes.>
My question is if males got fatter during conditioning as well as females.
<If they're overfed, yes.>
About 4 of them are quite a lot fatter than the other 3, and was wondering (hoping) that they where males and just benefiting from the extra feedings.
<"Extra" feeding is one thing, but there's a fine line between conditioning prospective parents and overfeeding them. The art to conditioning fish is to replicate the conditions that occur in the wild that trigger spawning.
Often this is things like the appearance of insect larvae in spring. So feeding live bloodworms or mosquito larvae can make all the difference. A bit more direct sunshine in the morning and adding some cold water (to mimic rainfall) are other tried-and-trusted spawning triggers.>
Thanks for your help!
<Cheers, Neale.>

Zebra Danio Babies -- 12/08/09
I have recently attempted at breeding zebra danios and have a bowl full of tiny danios swimming around. I have had them in here for a week now and would like to transfer them into a tank to have them filtered and heated,
though they are tiny and not sure how best to transfer them without taking the waste too.
<Not sure what you mean by this. Ammonia will be processed by the filter in the rearing aquarium, and solid wastes are largely harmless. So simply move them from the rearing aquarium to the bigger aquarium by scooping them out.
I find a plastic cup works best with baby fish. Fry are quickly killed by ammonia, so you shouldn't be keeping them in an unfiltered aquarium at all.
Temperature is relatively unimportant, and Danio fry will do okay in a (warm) home without a heater, down to about 18 C.>
Also I was wondering as they are so small (1 week old) whether they would be eaten if kept in a tank with platy fry (2 weeks old)?
<Should be safe.>
If so, another alternative is that my friend has a tank with two baby Malawi convicts and firstly wondered if these fish are vegetarians and whether they would eat the zebra babies/ and if suitable to share a tank together?
<No such thing as "Malawi convicts" as far as I know -- Convict cichlids come from Central America, and yes, these will definitely eat your Danio fry.>
Best Regards,
<Good luck (and well done!). Cheers, Neale.>

Zebra Danio Breeding... Biblioteca  4/6/2009
I have 5 Zebra Danios and 6 platies and i wanted to breed my zebra's so have moved them into my smaller tank. Of the zebras I think that I have 4 females and 1 male, so i guess i have my numbers the wrong way round...?
<Mmm, no... can work>
One of the females is quite a bit bigger than the rest and one of the females is still very small and young. I did initially move just the large zebra and the male into the small tank as I was led to believe you put just the two in a tank for them to breed?
<Mmm, no; not necessarily... though it's best to "just use" breeders in a given setting, as all can/will eat the spawn>>
this didn't work though, and instead it seemed the male was being chased by the large female and ended up hiding. so i moved the other 3 in also. however I have had no such luck at the moment and so am asking your advice?
the tank has a hiding rock and enough plants to hide, the water level is low, roughly 6 inches high and the bottom is filled with lots of small pebbles (purple colour so hopefully would allow easier finding!?). anyways
please could you advise on how best to work this?
<Work what?>
is it unlikely things will happen as i have only 1 male?
<Better to have more>
do they normally lay eggs in the morning?
if i have 5 fish in there will they get to eat all the eggs before i could discover them?
many thanks
<I'd be making a trip to the local library; checking out a couple of "olde" (as in print) books on freshwater fish breeding. There's a bunch more to this... in the way of water quality, temperature manipulation, conditioning of breeders, gearing up/culturing food/s for the young... Bob Fenner>

New found fry in tank (Brachydanio; repro.)  1/11/09 Hello, I have today found a number of fry that had recently hatched in my 35L tank. The sad thing is that I only found them when the water was going down the sink in today's water change! I have managed to save 10 or so (there may be more in the tank that I do not know of) but I don't know how to protect these few from being munched by the other residents of the tank. The other fish in the tank are 1 zebra danio, 2 leopard danio (these are the parents of the fry) 6 Trigonostigma hengeli and 1 Bristlenose catfish which is still only 3cm in length. I do have another tank (20L), however I do not have another heater or filter and so am unsure of how to rear these fish properly. It is still a relatively new tank at 6 months but the levels are ok and as it seems, the fish are thriving. levels are as shown; pH 7.5, Ammonia 0.6, Nitrate 5, Nitrite 0.1. Temperature is at 26'C/ 78'F So, to clarify how do I save these fry with what little equipment I have? Thank you for your help. Rachael. <Congratulations on your babies! The main issue with Danio fry is ensuring they don't get eaten. To that end, almost anything that stays at the top of the tank and keeps them separate from the adult fish is what you want. A breeding net or trap is ideal for this, and can be picked up for very little money. At a pinch, a net draped over the side of the tank with a few bits of gravel to weigh down the netting will do. I often use plastic cups around 5-10 cm in width and height, into which are drilled a few holes using a skewer. The holes mean that while the cup will float, water can move in and out, keeping the water inside the cup clean and warm. Any of these containers will work for the first few weeks while you grow on the fry. After 2-4 weeks, you'll want to move them into a tank suitable for rearing fish, realistically something in the 5-10 gallon range. While it is just possible to rear fry in a large breeding trap or net, in practise this is often a disappointing method as the fry eventually feel confined and try to jump out or simply get stressed and stop feeding normally. You don't want to add baby fish to a tank with adults until they're around half adult size; any smaller, and the risk of them being bullied or eaten is just too great. By the way, your nitrite level is too high: given the size of the tank, and the variety of fish you have, the chances are the tank is overstocked and/or under-filtered. Nitrite levels should be zero! Cheers, Neale.>

Danio Fry   12/10/08 Hello! Happy Pre-Christmas greetings to you all - hope you're not all credit crunched out! 2 weeks ago I bought 5 zebra Danios.. I stuck them in QT for a week, then into my main tank where they are a delight... I turned off heater and filter in the QT, and left it for a few days whilst busy over the weekend. I turned heater and filter back on Monday ready to clean the tank and settle in down for some more new arrivals (I am stocking a new tank slowly) I was about to empty water out of the tank when I spotted a tiny little moving line in my jug. On closer inspection of it and the tank I seem to have some 30+ (they move too much for me!) teeny tiny Danio fry. Today I spotted some were being taken into the inlet of the filter (the tank is a rekord 60ltr with a Juwel compact filter), so I have covered the inlet with a cut out piece of fine cloth, and rinsed fry off the top fine filter sponge back into the tank. Now I have to raise fry! What do I feed them on? I have some fine ground tetra food - is this OK? (I give it to the platy babies- but they are bigger) How long will it be before they are big enough to go in the main tank? (biggest fish here are platies) DO I need to have the filter running or can I turn it off whilst the are so very tiny(I am concerned about them being sucked in) What do I do about water changes - currently zero nitrite, zero ammonia and low (barely registered on my test strip) nitrate in tank. They are so small I cannot do a water change for fear of scooping them up. Is 26 C Ok? This is the tank temperature at present. I am delighted to have the babies, but have no idea what to do! It is not what I expected whilst they were in the QT! Your site is simply fantastic - and always a good source of help! Thanks again Sarah <Hello! Danio fry are relatively easy to rear on powdered/liquid foods, which is why they're so widely used in labs. (They're the fish equivalent of white mice.) The best food for the first week or so would be liquid fry food (e.g., Liquifry) though good results can be obtained with very finely powdered flake food sold specifically for baby fish (e.g., Hikari First Bites). Hard boiled egg yolk is another food sometimes used. Throw in some floating plants or thread algae as well, and the fry will peck away at the algae and infusoria they find there. After about a couple of weeks they should be well on their way to accepting finely powdered regular fish food. The main thing is not what to feed them, but how often to feed them. With all baby fish, the more small meals per day, the better. 4-6 meals is recommended. Cheers, Neale.>

Danio Fry  8/30/08
Dear WWM Crew,
My Danios laid eggs a few days ago. I removed all of the eggs and place them in a cup temporarily. They hatched yesterday morning. They are against the wall of the cup right now.
Can you please tell me what I should feed them and when I should start feeding them.
<Most fish fry will use their yolk sacs for a period of time post-hatching; you'll see that they have yellow blobs on their bellies and don't actively swim about. Instead they merely clump together, wriggling their tails to keep clean water flowing over them. Once the yolk sac has been consumed, then they start looking for food. In the case of Zebra Danios for example, this will be about 4-5 days after they have hatched.>
I read that when they came away from the wall that is when you should start the feeding process.
How do you make infusoria? I read that you make it by crushing green vegetables (like lettuce) and add it to the water. You then let the water sit until it becomes green (approximately 1 - 2 days).
<Pretty much. There are any number of methods using lettuce leaves and banana skins. The key is putting the "soup" somewhere sunny, because it's the sunlight that makes the algae grow, and the algae is what makes the infusoria grow. The 'Old School' method sped things up using Apple Snails, which for some reason seem to speed the whole process up.>
Also, I read that you can feed them with an eye dropper or a baster. Can I also chop up brine shrimp into little pieces?
<None of this is worth worrying about. Zebra and Pearl Danios are both easily reared using liquid fry food (such as Liquifry) or finely powdered flake food (such as Hikari First Bites). I'd tend to use the liquid food first, and the flake food after 1-2 weeks. Really, your problem won't be feeding them, but keeping the water clean. Baby fish need 4-6 meals per day, though those meals should be tiny. A simple pipette (of the type that comes with fish medications, for example) works great for adding food and slurping up uneaten food afterwards.>
I am in the process of setting up a fry tank with a sponge filter, heater and etc.
<Cool! Welcome to world of fish breeding... possibly the most rewarding (and ego massaging) part of the whole hobby, fancy saltwater reefs notwithstanding! Breeding and then rearing those fish to maturity is an objective test of your fishkeeping skills.>
Also, how often do I change the water of the fry tank?
<As often as practical. If possible, use a jug to take some water out on a daily basis. But at least a couple of 10-20% water changes per week would be recommended. Does rather depend on the size of the tank, filtration, number of fry, etc. If the water goes "bad" the baby fish will die quickly and in big numbers, so be cautious and err on the side of keeping the water extra clean.>
Please give advice. Thanks for you help - Jean
<Cheers, Neale.>

Zebrafish Development, lit. searches, scientific  7/17/2008 Hello, I am currently working in a Cell biology lab that is using zebrafish as a model system. What is the minimum temperature that a zebrafish embryo can develop? I have read that adult zebrafish can tolerate a wide range of temperatures (from 64-80F). I have also read that spawning is temperature induced. Is it possible for zebrafish embryos to develop normally in temperatures as low as 64F (since reproduction is stimulated by warmer temperatures?)? If not, what is the lowest temperature that normal development can occur? Thank you very much for you time! <Greetings. I'm assuming from your e-mail you're an undergraduate who's been assigned a project at a research lab someplace. That's great. Now, I do vaguely know the answer to this, but I'm pretty sure that putting into your project a factoid gleaned from "some guy on the web", even one with a PhD like me, isn't what your professors are after. What they want from you is to do a literature research. Trust me on this: being a some-time university professor myself, I know precisely and exactly what I expect from my undergraduates. So, what I suggest you do is first find out the scientific name of the Zebra Danio, and then use the bioscience/biomed literature search tools (e.g., SilverPlatter) at your academic library to access the scientific literature. Warning: the scientific name of the Zebra Danio has changed at least once in the recent past, so you will need to use both names to get the full overview. The developmental biology of the Zebra Danio has been done to death, and it was something being studied decades ago. So the answer to your question is certainly out there. Confused? Ask the librarian; librarians are happy to help with focused questions like this and will know precisely what tools are available to help you. In short: Good students use the scientific literature; Weak students use Google and Wikipedia. It's as simple as that. Good luck with your project! Neale>

Re: cichlids  Bob,  Hi, my name is Brenee King and I am a students of Mr.. Nordell's.  I was considering doing a project with Cichlids (Zebra Danio ?) <Hmm, Zebra Danios? These are actually not cichlids, but cyprinids (egg laying toothed carps, Brachydanio rerio I think is still their valid scientific name> having to do with their familiarity effecting their mating habits and wanted to know how often I could expect them to mate? Also how long it takes for the females to complete their cycle, mating and having their children? Please contact me when you have a chance. Thank You for your time and considerations. <Do put this fish's name in your search engines, go to a college library with the same... and start developing your working bibliography on this species biology. See the pieces on the site www.wetwebmedia.com on how to search the literature.. You will have more questions, need more answers than you have asked for here. Bob Fenner> Zebra Danio Q   3/10/06 Hey Bob! <June> My fiancée and I are looking forward to seeing you at IMAC (we actually met at IMAC last year and are getting married this June). <Congrats!> Any way, I'm currently working for a research lab that is working with zebra Danios <A fave test animal species in the sciences> (ophthalmology research) and I tend to keep the pH at about 7.2-7.6, but one of the ladies that works in the lab says that's too high and that their eggs are becoming coagulated (just with in the past 2 days).  She thinks that it's because of the pH. <Mmm, is possible... do you know the corresponding alkalinity? Might be better to blend more/some "just water" in the system here> Now, I have my degree in marine biology, and take my water chemistry results to heart, and to have someone double checking my results is insulting to me, so that is why I am e-mailing you to see what your opinion is.  The PI of the lab trusts me very much and hold me in high regard, but for some reason these ladies seem to not trust me.  Go figure. <They may have practical experience going for them here...> Any info you can give me would be very helpful as then I can have someone who has even more experience backing me up.  :-) Thanks again!! June PS:  Didn't know which e-mail address to send to, so I sent to both. <Ah, no worries. Bob Fenner> Siphoning Babies - Danio Fry and Gravel Cleaning - 09/30/2006 Hi Crew, <Hi, Mike!  Sorry for the delay....  your email wasn't able to come through properly in our Webmail system; my computer was able to read/respond, but I've been out a bit.  I do apologize for this delay.> I spend far too long reading your website but enjoy it immensely. <Heh!  Me too.> I have a mature 240 litre freshwater community tank and over the last few weeks, every time I do my weekly partial water change, I syphon tens of baby zebra Danios out with the tank cleanings. Obviously they are too small to net and I've tried various methods of separating them from the muck but, inevitably, I spend hours every week with my head in a bucket rescuing baby fish by whatever painfully slow method I've invented; dipping cup, air-tube syphon or pipette usually. <How about a brine shrimp net?> My problem is that I'm becoming increasingly fond of dumping the baby laden sludge directly into one of the fry tanks to save time. Although it's probably very good baby food, it does mean that I am building up waste in tanks that I can no longer syphon 10% of the water out of weekly since I'm back to square one - babies and muck. So what, if any, faster methods can you suggest of separating the babies from my siphonings please <A pipette and patience is probably the best/safest way....> and what is the best way of cleaning the gravel in the fry tanks?   <Best option here is not to keep gravel in your fry tanks.  Keep them bare-bottomed instead, if possible.> On a marine note, have you seen the new marine shop/website in Leeds?  www.reefranch.co.uk http://www.reefranch.co.uk/ ? <I haven't; I don't think anyone on the Crew right now is in the UK - but if I'm out that way, I'll have a look!> Fantastically well cared for fish and corals.   <Sounds great.  I like to hear of new, good shops opening up.> Best regards, <To you as well!> Mike Cursons <Wishing you well,  -Sabrina>

Breeding my Zebra Danios 8/10/07 I have a male and a female Longfin zebra Danio. I want to breed my Danios and the female appears to be full of eggs, but she seems uninterested in the male. I have a breeding tank, but I am not sure how to breed them. Can you please give me some advice? Thank you. <Greetings. Breeding Danios is not usually difficult. But as with any fish, you need to get the conditions right. You want slightly soft to moderately hard water, and the temperature must not be too high (about 22-24 degrees C) is ideal. Prior to spawning the fish, you should keep them cool, around 18-20 C, for a couple of weeks. Then warm the fish up, and start feeding lots of live or wet-frozen foods, perhaps 3-4 times per day. This is called "conditioning", and what you're doing is tricking the fish into thinking it is the breeding season. In the breeding tank, cover the substrate with glass marbles or small pebbles. What you want to create is a tank bottom where the eggs can sink safely out of reach of the parents. For spawning to occur, you need to add a small group of males and females, ideally slightly more males than females. It has to be a group, not a pair. These fish spawn in groups. Once they've spawned, you can remove the parents. The eggs hatch in about one day, but it's another 4 days or so before the fry are swimming about looking for food. Give them infusoria or commercial baby fish food (of the egg-layer, not livebearer, variety). The fry grow quickly and are basically hardy and easy to rear. Danios are among the best egg-laying fish for a first breeding project, so you should find them quite rewarding. Cheers, Neale.>

Are my Zebra Danios Pregnant? -- 10/28/07 Hi, I just bought 22 fish: 4 guppies (2 girls, 2 boys), 3 zebra Danios, 3 red eyed tetras, 9 neon tetras, and 2 mini catfish. They are all in one 30 gallon tank. Everyone has been getting along. One male guppy died, but now my 3 zebras have gigantic bellies. I didn't buy them like that and I have had them for about two weeks. How do you tell male and female apart for zebras? You see, I am 11 and my dad helped me put a tank together and tanks have been in the family for years. My dad and friend thinks that they may be preggers. But I am new breeding and I have only breed my guppy which had 4 babies. I don't want to start egg breeding. What should I do? -Thanks! Sarah <Hello Sarah. Danios don't get pregnant. But they will fill up with eggs prior to spawning. Males tend to be slender anyway, and a more yellowy colour; females are rounded and tend to be silvery. Danios are easy to breed, and are often considered the ideal species for beginner's to start with. If you want to breed them, you'll need to put pairs by themselves in another tank and let them scatter their eggs on the ground and among plants. Once they're done, you put the parents back. The eggs hatch after about 1 day, and the fry can be reared on liquid fry food. They grow quickly. If you don't want to breed them, don't worry about it. They'll lay the eggs, and the eggs will be eaten by other fish. Do check you aren't overfeeding the fish. Fish will also swell up when sick, though for three to do so at the same time is unlikely. Good luck, Neale>

... uh... FW... breeding... Danios? Zebras...   10/28/07 Hi, I e-mailed you guys earlier and I got a very good answer so I will come to you for now on. Well, you guys told me to put the parents in a separate tank and when they gave birth, to put them back in the big tank. The problem is I don't have another tank and I already went over my "fish" budget. <Ah, a common problem! There's really no workaround. Fish eggs are small and tasty (caviar!) and when dropped in a community tank other fish eat them. So you need to put the parents somewhere else, so you can remove the parents after spawning and protect the eggs yourself.> I also said that I didn't want to breed the zebra Danios. I really want to, I just don't know how. <Find an aquarium book on your next trip to the library; most will have a section on fish breeding. Danios are quite easy to breed. There's nothing difficult about doing it. You just need to be patient and follow each step in turn. Fish breeding is one of the best parts of the hobby. Watching a baby fish grow from an egg to an adult is a true wonder. If you don't have another tank right now, then save up and get one some time down the road. Danios live for several years, and the bigger they are, the bigger the batches of eggs you will get!> As I said in my other e-mail, I didn't know if my zebras are boys or girls, but now I think that they are all girls. <Oh dear.> But, I never bought them pregnant. <They aren't pregnant. They may simply be fat, or they may have eggs inside them. Without a male, they won't breed (obviously!).> So is it possible that my Male guppy mated with them also? <No. A Guppy is as distantly related to a Danio as a Gorilla is to a Tiger. Completely and utterly different. Guppies are livebearers (they give birth to live babies, like humans do) while Danios are egg-layers (like birds).> I have never seen him chase the zebras around. Could my red eyed tetras had mated with the zebras? <No.> please help! -Thanks! -Sarah <Just keep watching, learning and reading. Buy/borrow a book about aquarium fish. There's too much to put in one e-mail. Breeding fish is terrific fun, and warmly recommended as a hobby. Good luck, Neale.>

Ongoing Brachydanio repro.... reading  10/29/07 Hi, Do you guys think I could put just one zebra with a big belly in my breeder for a while? <No. For one thing it'll get stressed. Secondly, it'll probably jump out (or smash itself to pieces trying).> Because it is only a box with a "v" divider that can be taken out. How do I know if they are only a couple of days away from giving birth? <As I said in the last two e-mails -- Zebra Danios DO NOT GET PREGNANT! They lay eggs. They eggs will come out regardless. In a community tank, the eggs get eaten unless you find them quickly and rescue them. You can put the eggs in a breeder.> I mean, if they are pregnant I don't want them to give birth and then all the babies get eaten. <They won't 'give birth'. The eggs are dropped on the substrate. The eggs hatch, baby fish emerge, and for the first 24 hours or so basically don't do anything. After a day or so, the baby fish start swimming. In a community tank THEY WILL get eaten long before that happens.> Because I also want to see them grow up. <Hence the need for a breeding tank...> -thanks for your time and effort for me to have successful breeding! -Sarah <Read up on fish breeding. It's fun, and quite easy. But there's no "short cut". You need a second tank for egg laying fish. Goo luck, Neale>

Pregnant Zebra Danio 10/2/07 Hello, <Hi there> I have a 55 gallon tank with a 13 inch ?Plecostomus, <Yikes! Needs more room... or to be traded in for a smaller individual> 3 zebra danios(2 females, 1 male).? My? problem is with one of the female Danios.? She appears to be very very pregnant.? She is huge.? Her skin appears to have cracks? running down the side and underneath her belly.? She is eating and swimming.? She will not release any eggs.? I am assuming that is what she should be doing. Do you have any advice on what I could do to help her out?? It looks like she is going to explode. Thanks, Julie <Likely some sort of gut blockage... what do you feed and how? Please read here re possible Epsom Salt treatment: http://www.wetwebmedia.com/FWSubWebIndex/saltusefaqs.htm Bob Fenner>

Re: Pregnant Zebra Danio... Lg. Pleco in small world  10/3/07 Hello, <Hi there> Thank you for your reply about my problem with my pregnant Danio. <Welcome> However, I was taken back by your response to me having a 13 inch Plecostomus in a 55 gallon tank. <Yes... the fish is as long as the width of this tank...> I don't have the tank over loaded with plants or decorations so he moves around easily. <Mmm... do you know which species of Loricariid this actually is? There are some that would/might be stunted here...> I see him swimming on his side, upside down, enjoying the bubble curtains - eating the algae all over the tank. He "appears" happy and able to move around freely. I have moved him from a 10 to 20 to 55 gallon tank as he has grown from 2 inches to 13 inches in the last 4 years. I am a novice at the Plecos and didn't have any idea of what I was getting into. Could you explain this to me in a little for detail please - this fish has become a part of my family - my husband thinks I love the fish more than him (haha)- as I sit and talk to the fish and just watch the fish's personality unfold daily. Thanks, Julie <Do take a look on fishbase.org re the family... some of the species listed... This fish really does need more room still. BobF>

Zebra Danio egg question   12/31/07 Hey, <Hey?> When I went to go feed the fish this morning I noticed some small black dots an my live plants. Could they Be Zebra Danio eggs? <Possible but unlikely. Fish eggs are usually 1 mm or so across, transparent, and with a jelly-like appearance. As they mature, you should soon see the embryo. By all means remove the eggs and place in a floating breeding trap to see what happens. But there are other things they might be -- snail eggs, planarians, silt, etc.> -Thanks! -Sarah <Cheers, Neale.>

Re: Zebra Danio egg question   12/31/07 Ok, You said to put the black things in a breeding trap. I am borrowing one from a friend and right now it has 12 baby guppies in it. Will the guppies eat them? <Certainly possible. You could improvise a breeding trap of some sort using a plastic cup with some small holes punctured through it to let water diffuse in and out. Use your imagination. What you're after is something that floats, keeps the eggs safe, but allows for a slightly flow of water without the holes being so big the baby fish (if any) would escape.> I'm also wondering, could it be a different kind of algae? <Maybe. Without a photo, "small black spots" are difficult to identify.> There doesn't seem to be a jelly-like substance around them. And they are at least 1/4 of a centimeter apart. <Doesn't sound much like fish eggs.> -Sarah <Cheers, Neale.>

Re: Zebra Danios egg question 12/31/07 Hi. I tried to take a picture. see what you think. Thank you. Sarah <Hello Sarah. Not sure at all what these are! They don't look like Danios eggs to me, but who knows? Could be some sort of insect eggs. Out them into floating thing and see what happens. Keep us posted! Neale.>

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