Bronze Cories Dying Suddenly Help

Discussion in 'Corydoras' started by Deku-Cory, May 7, 2019.

  1. Deku-Cory Valued Member Member

    Even though the fish in question have passed, I’m going to use the sick fish template since it helps organize all important information.


    What is the water volume of the tank? 75 Gallons
    How long has the tank been running? Since February of 2019, have had fish longer.
    Does it have a filter? Yes, a sponge filter, Marineland Biowheel 200, Cascade 1000 Canister Filter
    Does it have a heater? Aqueon Pro 150, Aqueon 50w
    What is the water temperature? 76, stays constant.
    What is the entire stocking of this tank? 3 (Was 4) Adult Bronze Corydoras, Roughly 30 adolescent Bronze Corydoras, 4 Peppered Corydoras (Yes I know I need more.) A variety of live plants.

    How often do you change the water? Once a week.
    How much of the water do you change? Usually around 20-25%, sometimes more.
    What do you use to treat your water? Tetra AquaSafe, Aquarium Co-Op Easygreen (Has no copper.)
    Do you vacuum the substrate or just the water? Vacuum the substrate every water change, occasionally moving decor to clean underneath.

    *Parameters - Very Important
    Did you cycle your tank before adding fish? Yes, Marineland filter was brought over from old tank along with substrate. Tank went through a small cycle but quickly settled.
    What do you use to test the water? API Master Test Kit
    What are your parameters? We need to know the exact numbers, not just “fine” or “safe”.

    Ammonia: 0
    Nitrite: 0
    Nitrate: 20-40
    pH: 7.6-7.8 depending on the time of day and water changes.

    How often do you feed your fish? Once a day.
    How much do you feed your fish? 12 wafers broken into pieces.
    What brand of food do you feed your fish? Hikari Sinking Wafers
    Do you feed frozen or freeze-dried foods? Omega One Frozen Bloodworms once a week. Portion defrosted in tank water, package is immediately returned to freezer to prevent defrosting.
    No new food has been opened recently.

    Illness & Symptoms
    How long have you had this fish? Adolescents were 10 months old, raised from birth. Adult has belonged to me for about 5 years old.
    How long ago did you first notice these symptoms? First adolescent died a few weeks ago.
    In a few words, can you explain the symptoms? Sudden death without any symptoms.
    Have you started any treatment for the illness? No.
    Was your fish physically ill or injured upon purchase? No, have all been healthy.
    How has its behavior and appearance changed, if at all? No change.

    Explain your emergency situation in detail.
    Over the past few weeks I have found 2 dead adolescent Bronze Cories. I was worried but I didn’t know what could be done. This weekend I found one of my adult females Bronze Cories dead, I was devastated as I have owned her for years now and it was very sudden. It is important to note that the adult is not related to the adolescents, another unrelated female is the mother of all of them. The most concerning aspect is the identical nature of the deaths. All 3 died very suddenly with no signs of illness, all were on their side on the bottom of the tank with pristine bodies. None showed any signs of injury or stress before or after death, all had full bellies, long barbels, perfect fins, no wounds, and had been active and curious without being frantic or stressed.

    I can’t think of anything that would strike down fish without a single symptom over a period of time instead of all at once. Parasites and disease would show body deterioration before death. Issues with the water would show stress, and I believe the impact on the population would be more widespread and sudden. The only things I can think of are that the water source has something going on, or that my nitrates have been slightly elevated while I’m figuring out fertilizing. (As mentioned above, the fertilizer I’m using has no copper and is assured to be safe for all fish and inverts.) Would the slight Nitrate problems be the cause of this?

    Maybe there is no answer. Maybe it’s all just some cruel, cosmic coincidence. It’s just difficult, I love my fish and I feel like I’m failing them because I can’t help them. I also so badly want to add new fish to the aquarium but I can’t in good conscious do it right now. I just thought it would be a good idea to make a post in the chances that someone knows something that I’ve missed. If there’s any details you need, let me know. I also have pictures I took of the adult female shortly after I found her, but you really can’t see much of anything. I included them regardless just in case it helps. Thank you so much to everyone who read through all of this text.

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  2. RyanC14 Valued Member Member

    Corys generally have a lifespan of about 5 years. The adults may have died of old age. I'm unsure of the adolescents, but sometimes fish will just die for no noticeable reason. Maybe do larger water changes just in case though. I'm very sorry for your loss.
  3. DoubleDutch Fishlore Legend Member

    Most Corys have a lifespan of 25 + years Ryan, so I doubt it is old age.

    Bronze are pretty hardy, so quite difficult to tell what's wrong in this case.
  4. Redshark1 Fishlore VIP Member

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  6. DoubleDutch Fishlore Legend Member