HELP: Sudden death of corydoras

Discussion in 'Freshwater Fish Disease' started by Ayrigosa, Aug 9, 2015.

  1. AyrigosaValued MemberMember

    In the past 4 days I've had two corydoras die.

    They're in a 10G

    The temperature hasn't changed drastically and the water is fine.

    I have a Molly who won't stop wiggling, I think she may be attacking the smaller fish as my tetras have torn fins.

    No evidence of this on my BN pleco, but she hides 99% of the time.


    Is there any illness that wouldn't show other than maybe being a little skinny? They're being fed plenty (algae wafers etc.)

    Also I've had them for 4 months and nothing new has been added to the tank since their arrival, yet they both died this week.


    We have one corydora left and I don't want her to die too. :(

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  2. TikiBirdWell Known MemberMember

    Hi Ayrigosa! I'm not an expert, but I do think cories need a partly meaty diet, since they're omnivorous. Do you feed sinking catfish pellets as well as the algae wafers?

  3. AyrigosaValued MemberMember

    They get tropical flakes and cichlid pellets right now. But my pleco tries to eat everything I put on the tank bottom.

    They lived for 5 months like this, so I don't think it was a food issue.

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  4. Dom90Fishlore VIPMember

    10G is way too small for the fish you have, and they have high bioloads, the mollies and the BN pleco. What are your water parameters? Do you have a test kit to check?

  5. AyrigosaValued MemberMember

    .... Molly. ONE.
    It's not bloody overstocked.

    6 fish is not overstocked when only one is large.

    The only fish over an inch is my pleco and the water is fine.

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  6. Dom90Fishlore VIPMember

    It's not about the size of the fish but also the bioload that you have to take into consideration. None of the fish you have would work in a 10g.

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  7. Bijou88Well Known MemberMember

    You also have to take their adult size into consideration, bn plecos and mollies can both get upwards of 5" when grown. Two 5" fish with high bioloads in a 10 is most definitely over stocked.

    Also, just because your cories survived for months being fed what they were fed, doesn't necessarily mean they were getting adequate nutrition from it.... (not trying to sound mean here, but it's true). My pleco also tried to hog all the bottom feeder food, I just feed him his shrimp pellet first and then drop a couple on the other side of the tank for the cories, it seems to work fine.

    I'm sorry for your losses :( hopefully you can save your remaining guy.

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  8. BornThisWayBettasFishlore VIPMember

    Hi there! Such a cute angelfish in your avatar! :D

    Yes, your tank is overstocked, I'm afraid. Depending on the type of molly you have, they can grow rather large. Also, the BN pleco not only will grow but are also high waste producers, and most tetras are too big/active for a 10g, except in the case of ember tetras, and no cories will fit comfortably in a 10g either.

    The problem with an overstocked tank is that it can lead to many issues, including aggression, sickness, water parameter issues, and sometimes one of those things can even lead to death, sadly.

    Can you get your water parameters tested somewhere? Or buy your own liquid test kit? Make sure to ask whatever store you take the water to if you get it tested what kind of test kit they use.

    Now, for the cory. I'm currently feeding mine Hikari Tropical Sinking Wafers for Catfish, Loaches, and Bottom Feeders. If yours aren't getting enough because the other fish are stealing it, I've been told to feed mine at night after lights off, and to crumble the wafers before sprinkling them around the tank. If food is the issue here, fish can go a surprisingly long time without food, and maybe yours were just surviving off what you were giving them because no other options were available right then. TMK, cories are carnivores.

    Let me know if you have any more questions and I'll do my best to answer them! :)
  9. AyrigosaValued MemberMember

    The water is fine or I wouldn't be posting...

    The pleco is already full grown and the Molly is small so NO it's not overstocked. It's been set up the same way for over a year.

    Also the angelfish passed away. Heater broke.

    The only PROBLEM in my tank is a snail infestation.

    Thanks for NOT answering my question at all and implying I know nothing about fish. This was a post about illness.

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  10. SaturnValued MemberMember

    Ayrigosa, we are not trying to attack you :)

    We are just pointing out that the circumstances your fish are in may not be the best for them. HOWEVER, it is your choice on what you want to do with your fish/tanks, we're just trying to help you and inform you.
  11. lbonini1Well Known MemberMember

    Ayrigosa, they're only trying to give you guidance and though your post is about illness, the tank being overstocked may have led to your cories dying. We're not implying you know nothing about fish so please don't put words into our mouths. You can choose to take the advice or not, we can't force you. But don't attack us for no reason.

    Thank you.
  12. BornThisWayBettasFishlore VIPMember

    Sorry for your loss. :(

    And I'm sorry, we just need more tank stat info before we can make a safe diagnoses. It's like telling a doctor that you're sick and to just prescribe you something. The doctor doesn't know what's wrong unless you tell him and if he just prescribes you something it very likely won't work and can even be harmful (even to the point of devastation). Also, I did give you a recommendation for food.
  13. AyrigosaValued MemberMember

    I forgot I'd explained about the water and stuff on a different post. (Facebook)

    Anyways all the levels were good tested with chemicals not the sticks.

    The tank has only tiny fish, they'll be moved to a bigger tank when they're larger the only big fish is my pleco.

    One inch per gallon.
    I'm below that.

    I have a 20G it's cycling.


    I had some swordtails die of a bacterial thing but that was a while ago and no tank parameters changed while they were in it for 4 months. They just both died suddenly one week.

    The rest of the fish, excluding my Molly (she's had issues for a while) are perfectly healthy and happy.

    The cories were getting tropical pellets for angelfish/discus etc. And algae wafers and flake food.

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  14. AyrigosaValued MemberMember

    And if you don't want to seem like you're attacking don't post like you know everything when there's a lot of things you don't know. Like the fact my pleco is already full grown and small or the fact my Molly is young still and small.

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  15. BornThisWayBettasFishlore VIPMember

    The one inch per gallon rule is actually pretty inaccurate, as it doesn't take into consideration the activity level, bioload, and schooling/tankmate needs. :)

    Imo, it is possible that they weren't getting proper nutrition. Cories are carnivorous tmk, which means the algae wafers wouldn't have worked well for them. Did the flake food sink? Can you link me to the angelfish/discus food you used for them? I'm using sinking pellets/wafer specially designed for bottom feeders, and it's not algae wafers.

    Also, I'm well aware that I don't know everything, but I'm very eager to learn! :D
  16. GekcoWell Known MemberMember

    From what I see nobody here is acting like they know everything, all they are doing is give you some advice on what they feel is a good approach to your current situation.

    Regardless BN Plecos grow up to 6 inches so if your pleco is still small in my opinion it is still growing up. Also a BN Pleco is recommend to be in a minimum of a 30 gallon tank and a molly is recommended to be in a minimum of a 20 gallon tank.
  17. happygoluckyWell Known MemberMember

    You seem to not enjoy being told what to do, but IF I were you I would dump some Tetra SafeStart into the 20g, and add your remaining corydora. Then I would fill in the school(of whatever kind of cory you have, the EXACT SAME species). This is not exactly the best situation, but it'll have to work. Once your tank has finished the 2 weeks, wait a little more, then pick out a nice centerpiece fish such as a Dwarf Gourami. Then, you could possibly add 3-4 guppies, all one sex(this depends on your DG temperment). That is a fully stocked tank.

    Good luck, and try to remember everyone on here is trying to help you help your fish, nothing else.
  18. Bijou88Well Known MemberMember

    If I recall, it's usually 20g for balloon mollies and 30 for regular ones but I may be remembering wrong.

    I don't feel that anyone was attacking you, we're all trying to offer advice for feeding your cory and keep your other fish comfortable, I find it doubtful that they are atm. If your molly is over a year old and is less than 1", it's likely stunted as it should have grown more by now....

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  19. junebugFishlore LegendMember

    That doesn't tell us anything. What are the actual numbers for ammonia, nitrite, and nitrate? What is your pH? What is your water change schedule?

    Your pleco is certainly not full grown, unless he's at least 5" long. More than likely, he's stunted, like your molly will soon be. As a result of both of these fish being in the tank, along with the prior resident of an angelfish, your water quality can't possibly be what it should be, which is a HUGE contributing factor in the death of your cory. Even assuming that your ammonia and nitrite are both 0 and you've managed to maintain some semblance of a cycle, the TDS in this tank must be off the charts. Most fish are sensitive to extremely high TDS, catfish in particular, it seems. This will have caused all sorts of issues with your cory, and likely explains the death of your angelfish as well.

    Everyone who has replied has answered your question pretty explicitly. Your tank is severely overstocked (I realize you don't like hearing this, but it's very true). This key component has, either directly or indirectly, lead to the death of your cories.

    Simple facts here: Mollies grow to be 5", often even larger if they're females. They are massive waste producers. BN plecos, assuming yours is a common ancistrus, will also grow to about 5" and is a massive waste producer. Cories are active swimmers, and carnivores, so not only have they not been getting the nutrition they need, but they don't have any room to swim. They're also shoaling fish, and you only had 3 of them from the sound of it. They really should be in groups of 5 or more, which makes a 20 gallon tank the absolute bare minimum for them.

    BN plecos require at bare minimum a 20 gallon tank. Mollies require AT LEAST a 20 gallon tank, assuming they're a tiny variant. More than likely your Molly is not one of the tiny variants and as such will require at minimum a 30 gallon tank.

    With all of these contributing factors, unfortunately, it's no surprise that your cories got sick.

    Hopefully you will be able to upgrade to a larger tank ASAP and get the fish into it, which will help on the road to getting them healthy again. Once everybody is 100% healthy, you can use your current 10 gallon as a quarantine tank and get some more cories to fill out your school.
  20. lbonini1Well Known MemberMember

    1. I agree with happygolucky, either re-home some of your fish or stock them in the 20g.

    2. Based on your profile, you have a 10 g with 2 Single-Tailed Goldfish, that is also overstocked. Please correct if this isn't true.

    Last edited by a moderator: Aug 15, 2015

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