Evil, Evil Zebra Danio's

[Jan Cavalieri]

I have (or had) a group of seven that delightfully schooled very well. So much and at such speed that the rest of the fish in the tank just had to get out of the way.

They are described everywhere as "peaceful schooling fish".

Buried in a book I read that they are also known to be fin nippers. I discovered one of my favorite Gourmies with all his fins bitten off - all in a matter of one night (I do a head count twice daily). Poor thing was laying on his side at the bottom of the tank breathing heavily. I picked him up and put him in a cupful of tank water and fed him some of my morphine (yes, I am a drug addict LOL), I think that killed him but just in case, I added Ice and put him in the freezer. Somebody suggested clove oil - where do you find this? I checked one grocery store in person and two online and none of them carry it. For some reason I just knew it was the Zebra's - their behavior is not exactly peaceful but very high energy - two died in my care after running into the gravel filter. They chase each other constantly and have a tendency to pick on the smallest Zebra.

I bought a new tank - everyplace was out of decent 5-7 gallon tanks for these guys (yes I know a bit small but they'll be OK - it's way more space than they have in my 29 gallon to school. So I ended up buying another 29 gallon that was on sale, equipped with the regular crappy filter and heater. Boy are the zebra's loving that - bought some foilage and stole from my other tank. Bought some decorative stuff with lots of places to hide. Besides using Prime to get rid of the chlorine and chloramines I used "Stability" to avoid "the new tank syndrome" Also added some gravel from the other tank. My numbers have been decent. Catching the Zebra's about killed me. Finally decided it was best to use my biggest net and it worked.

So they were happy schoolers - until today - I left the house for about 1 hour and came back to find one partially eaten Zebra - fins eaten off (these are the long finned zebra's) . His gills looked bloody as did his head - and he was the smalled Zebra as best I could tell.

So originally I was just going to add more fish to the 29 gallon, leaving these guys plenty of room to school but now I've decided they won't live peacefully with any fish with fins so I'm going to continue to look for a smaller tank for them and use the 29 gallon tank for something more interesting. Once all the zebra's have killed each other I'll turn it into a hospital tank or something. I'll do a full cycle on both tanks since there is no hurry. Does this sound like a good plan?

Oh - one more thing - while their water numbers are good (Ammonia 25, Nitrite 0, Nitrate 5.0, Ph 7.4, GH and KH both 50-100 ppm - supposedly good for tropical fish). But their water is VERY cloudy. I'm thinking 1. I didn't wash the black gravel well enough or 2. I'm overfeeding or 3. Since I didn't wait for the tank to fully cycle it's a cycling anomaly. Any ideas? I really HATE looking at it since it says FAILURE all over it. Thanks in advance for your help. Feel free to beat me up for not cycling first - but I didn't want a tankful of finless dead fish.

 

[FishGuest5123]

I’m sorry for your troubles but laughing hysterically at the same time. I’m having the same issues with guppies. They nip each other’s tails to shreds so I take the injured ones out and place them in clean salt water QT tank. I was going in circles taking one group out of QT and putting a new group in. I finally unplugged the QT tank and placed them all back in the community tank. “Only the strong survive” is my new motto for that tank. Good luck! Oh, you can get Clove oil in essential oils or with aromatherapy stuff. EBay has it under essential oils and then you choose the type you want which will be the Clove oil.

 

[Colin_T]

Can you post pictures and a short video of the fish?

For 2 fish to lose both fins and die in a couple of days, it sounds more like a disease than fin nipping. And Zebra Danios are not renown for their fin nipping, at least not in my experience. They are very active fish that race around everywhere but I have never seen them nip fins.

Do not add new fish to any tank that has had a fish die in during the last month. If there's a disease in the tank, any new fish will only make the problem worse. New fish can also introduce new diseases that can wipe out fish that are weak or sick.

Do a 75% water change and gravel clean the substrate each day for a week to help dilute any disease organisms that might be in the tank.

Is your ammonia test correct (25)?

 

[Lunar Jetman]

Is your ammonia test correct (25)?

I wonder if he means 0.25

If this were my tank I'd be carrying out water changes until Ammonia was 0 as this could be making your fish ill and then they're getting picked off by their more healthy tank mates.

 

[Jan Cavalieri]

Deanasue - thant's for the tip about clove oil. I'm a baker so I was looking in the baking department. I'll try ebay or amazon.

Colin - you want me to try to do pictures and a video of both dead fish? I just tossed the fish. Actually the Zebra that died is- I think- the smallest one that has been tormented by the main zebra for a long time but it's hard to tell once they are dead when they all look alike. I should have been more specific, only his long bottom fin was missing, as far as I could tell. He didn't have huge side fins, they could have been gone too but I didn't notice - it looked more like an attack on the head and gills (or he ran into something). There was a lot of red under his gills and head. So he's and his kind are in the new tank. Sorry about the Ammonia reading - it was .25 Another Dani died recently when they were in the other tank - I never could tell if that was murder or an accident but I found a Dani stuck in the filter tube, blocking the filter. His entire side was mutilated but I couldn't tell if that was done on purpose or just a death and he ended up in the filter tube - no fins were missing but that's when I started paying attention to how the largest Dani bullied all the fish - but primarily went after other Dani's;

Now when all of them were in the same tank together, the other fish that died was a terribly shy Gourami that was bullied by one of my other Gourami's from the minute he was put in the tank but eventually he was left alone. The Gourami that bullied him bullied all the Gourami's - they would just get out of his way and he'd stop - he mainly bumped the others with his head, preventing them from eating. I never saw him bite anything. The zebra's also picked on the bullied fish, the main bully in the Dani group constantly tried to nip his back fins or the back fin of his schoolmates - including the little Dani (I think) that died in the second group). The attack on the Gourami's was all on his fins - they appeared chewed off with ragged ends. Both the bottom, top and sides and he was a large (2 1/2"-3" fish. It happened overnight; The Dani that died had his main tailfin chewed up but no side fin damage and a lot of head and gill injury - either from head butting or him hitting the wall.

Last time I was at the pet store I bought some frozen krill. Defrosted it in a cup and fed both tanks. Looks like tomorrow I'm going to have to remove most of it from the tanks - nobody seemed to care for it. What do you and everybody else feed their fish?

 

[Jan Cavalieri]

Oh as far as the low ammonia - the day before it was zero. That was the new tank - I did no cycling on that tank at all so I was happy to not have any greater ammonia readings. I just wanted to get the Danio's out before they killed any more Gourami's. The ammonia level in the first tank where the Gourami was killed was zero.

 

[Jan Cavalieri]

I found an old post from 2003 titled: "My evil zebra danios bit my neon tetra's tail off". The tetra did later die. I do have one reference from a kindle book I bought that mentions that zebra danios are often known to nip off fins. If I had known this I would never have bought them - but frankly they are crazy cute - swimming at 100 mph and chasing each other - but some times that chasing leads to a little extra aggression which is why I think the Zebra (while in the new tank) died - part of it was eating his bottom fin off and the other part was persistent bullying by the largest Zebra - he may also have just run into the wall of the aquarium given the head and gill injuries. I just dread waking up in the morning to see if any other fish have died or been injured. I picked these species out to be together based on reports that they are all PEACEFUL fish. That appears not to be the case. Thank goodness my Raspdorias and Cherry Barbs are completely peaceful and they don't get picked on either - they just wisely stay out of everybody's way.

 

[Colin_T]

Photos of the remaining fish please.

Do not leave uneaten food in a tank for any time. Once you have finished feeding the fish, remove uneaten food straight away because it will cause the ammonia levels to go up rapidly.

 

[Jan Cavalieri]

I'll see what I can do to get pictures of the danios - they swim very fast. I know I should have removed the krill immediately but I gave it to them late in the evening so I thought maybe they'd munch on it once I was out of the room (and in the other tank with the bigger fish they did eat most of it but I still need to remove several). Plan to remove as soon as their lights are on this morning. I should have known better to start a food like that at night.

 

[Byron]

I believe I did explain the Zebra Danio issue previously in one of the other threads. Your first problem was too small a tank, then an inappropriate combination of species, then too few danios. Nothing else.

Sedate fish like gourami cannot be combined with active fish like danios. When you do this, first it stresses out the gourami, and like all fish they release chemical signals (pheromones and allomones). The danios pick these up, and respond--usually with physical aggression. Then they nip fins, because it is fun to do when you're a bully.

Second, danios are a shoaling species and that means they must have a group and sufficient space. You cannot keep this species in a tank less than 30 inches length (a long 20 gallon or a basic 29 gallon for example). Even this is minimal. Seriously Fish recommends at least a 90 cm (36 inches) length tank. There is good reason for this.

The fin nipping among the danios now is due to insufficient numbers and too small a tank. That's it. And once fish turn aggressive because of the environment we have forced them into, they do not change. This is because the aggression is the fish's response to severe stress and once it goes over the edge like this, the damage is done and irreversible.

Before I leave, a comment on fish euthanasia...your clove oil, freezing, etc is cruel to the fish. There is only one quick way to kill a fish, and that is to net it out into a folded paper towel and give it a couple good whacks. Dead in a split second, no suffering, no problem. This method was listed as the most humane and effective in an article in Amazonas magazine, and I believe also in Practical Fishkeeping.

Edit: the cloudy water is most likely a bacterial bloom. Not a problem, it will clear as the many species of bacteria become established in the substrate.

 

[Jan Cavalieri]

Ok - see if this pleases everybody. They are currently in a 29 gallon tank all alone. Tank has not been cycled but I added Prime to the water and Stability (to "avoid the new tank syndrome"). PH is 7.2 KH and GH are both at 3 dropfuls leading to 50 ppm. Nitrites, Nitrates are both zero. Tank is cloudy white and with a lot of bubbles at the top (probably O2 bubbles but it looks like soap) as far as I know, no soap has touched this tank. The Danio's were mentioned to me as one of about 15 different combinations of fish that would work well together in a 29 gallon tank. No word that they were so boisterous or that they were fin nippers (as found in other posts here and in other books I've read). You could tell from day one there was always a hierarchy and when I needed to replace most of them, they re-established the dominance. So the dead fish I threw away is truly dead, but just after taking pictures of the tank and then doing water testing (and BEFORE I ADDED ANY CHEMICAL) I turned around and saw yet ANOTHER DEAD ZEBRA. Hard to tell if there was any physical damage - his bottom fin did look a little out of sort but the biggest thing I noticed was blood coming from the gills and head, which ended up covering my fingers. So I cannot tell if he was "picked on" by other Zebra Danio's or it was suicide. After I tested the water I found .25 in ammonia (same as the other day) and 0's on everything else - the GH and KH were both at 3 drops indicating about 50 ppm. I'm attaching the zebra's in motion (this tank doesn't have a back cover on it yet so it's hard to see) and a picture of the most recent dead one. As far as humane euthanasia. In my lab days I had to cut off the heads of rats. By the time you get to the 20th or so rat they could smell it in the air and rat 21 and so on are totally freaked out. That's a fast method but hardly psychologically humane. Killing anything that wasn't supposed to die is hardly humane but in the case of "too physically ill to live" that's a completely different subject. I still couldn't do it with a book, but I believe I overdosed it with morphine and anybody that has observed as many critically ill friends and family involved with Hospice and you learn quite quickly they are overdosing them - to the "outside world" it looks like natural death - they become non-responsive, slack jawed, organs start shutting down - then take a look on the chart and you'll see extremely high levels of morphine, fentanyl, hydrocodone, - what ever the patient is used to getting because as soon as they go into hospice the dosages start increasing. It's a big façade but I think I could argue it's fairly humane. At least if I die "naturally" I hope it's with the help of some big doses of morphine (I am terminally ill BTW) do don't recommend fish that live longer than say, 10 yrs. (actually my daughter loves fish so that may not be a huge problem). I intentionally adopted an elderly cat and have already turned over my much loved 14 yr old parrot to an amazing sanctuary, where he appears to be very happy and I can visit any time (unfortunately I rarely drive any distance because of my narcolepsy) but I get pictures and video's of him on facebook constantly. Anyway, my point is that I don't deal with death well any more (in the last two years, both my parent have died as well as my husband and Basset Hound Dog that I adored) and them I'm dying too so I'm not smacking anything with a book to kill it - although the snails are becoming VERY tempting since I can't even razer blade off their infertile eggs covering the inside of aquarium number 1.

 

[Colin_T]

please use paragraphs to make it easier to follow

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The fish appear to have a bacterial infection (red patching on the body). They also have very red gills that are flared out. This can be from chemicals or bacteria.

Anti-biotics are probably required for this. Make sure you remove carbon from filters when treating so it doesn't remove the medication.

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White foam on the surface can be caused by iron based plant fertilisers.

 

[FishGuest5123]

I believe I did explain the Zebra Danio issue previously in one of the other threads. Your first problem was too small a tank, then an inappropriate combination of species, then too few danios. Nothing else.

Sedate fish like gourami cannot be combined with active fish like danios. When you do this, first it stresses out the gourami, and like all fish they release chemical signals (pheromones and allomones). The danios pick these up, and respond--usually with physical aggression. Then they nip fins, because it is fun to do when you're a bully.

Second, danios are a shoaling species and that means they must have a group and sufficient space. You cannot keep this species in a tank less than 30 inches length (a long 20 gallon or a basic 29 gallon for example). Even this is minimal. Seriously Fish recommends at least a 90 cm (36 inches) length tank. There is good reason for this.

The fin nipping among the danios now is due to insufficient numbers and too small a tank. That's it. And once fish turn aggressive because of the environment we have forced them into, they do not change. This is because the aggression is the fish's response to severe stress and once it goes over the edge like this, the damage is done and irreversible.

Before I leave, a comment on fish euthanasia...your clove oil, freezing, etc is cruel to the fish. There is only one quick way to kill a fish, and that is to net it out into a folded paper towel and give it a couple good whacks. Dead in a split second, no suffering, no problem. This method was listed as the most humane and effective in an article in Amazonas magazine, and I believe also in Practical Fishkeeping.

Edit: the cloudy water is most likely a bacterial bloom. Not a problem, it will clear as the many species of bacteria become established in the substrate.

I just can’t whack them like that. I’m a wimp, what can I say?

 

[PheonixKingZ]

I thought u couldn’t, until I tried to rescue a dwarf Gourami (flame) form a terrible PetCo fin rot “incident” and I had to kill him. I just took a rod of metal, and with one quick, “whack!” He was gone. If you can’t or don’t want to do that, then use Clive oil. If you put a fish in the freezer, ice shards might clog up there gills, and they will suffocate. Clive oil, or “whack-on-the head-“ technique, works much better. I hope this helps.

 

[Back in the fold]

What ! Zebes are awesome. They really should be kept to themselves. If they are in a tank that gets a little direct and indirect sun you will see that that blue color on them is really pretty. Super easy to induce spawning and fairly easy to raise the the fry although they are very very tiny. The old standbys of the hobby, of which Zebes are one, are still the nicest fish. Devote a big tank to a big school of them for a real treat. All the Danios are great. I like Leopards too. And the Giant Danio is an awesome fish. Love your Zebes.