Fish Suddenly Started Dying After Getting New White Mollies.

Discussion in 'Freshwater Beginners' started by Allilang, Apr 22, 2017.

  1. AllilangNew MemberMember

    Classroom fish tank

    Tank: 60 liter (16 gallons) 3 weeks old, Filtered, 28 degrees C
    Water change: every 2-3 days with water that has sat for the same amount of time to reduce chlorine

    guppies 6
    platies 6
    cory cats 3
    neon tetras 3
    white mollys 2 + 3 introduced
    black mollys 2 (died)
    1 baby molly (I didn't know mom was pregnant when I bought her and i was only able to save one)

    The fish were all happy. until my black mollies died. One wedged herself behind the breeding box on the weekend and the other developed white fuzz or something then died a few days later. both tended to hide behind the sponge filter. I would have to tap the glass to scare them out for feeding time. However, the one that developed the fuzz became more active after becoming sick.

    After they died I got 3 new white mollies because my other two were doing so well, and my students liked to watch them the most. The next day one new molly was dead and two guppies with it. Then during an 8 hour day, 3 more guppies and the two healthy original white mollies died. The cory cats and the neon tetras seem to be unaffected. the next day no new fish died, but one guppy and one platy seems sluggish. Both mollies have little appetite. The baby molly is in a breeding box alone and seems healthy.

    I went back to the store and she said hers didn't die and claimed that it was on my end. I have been taking very good care of my fish and had no fish die for weeks. I live in Korea, and I cannot find any water test kits here. However, judging how the tetras and corys seem immune, I think It must be a disease the new mollys brought.

    I have a second tank with semi-aggressive species and all are healthy.
    1 chinese algae eater
    5 albino tiger barbs (they look like nemo so I had to get them)
    3 black skirt tetras
    2 red eye tetras

    Can anyone shed some light on what may have happened? The sick molly was sick for at least 4 days while all my fish became sick and died within hours. they suddenly become lethargic and sit on the bottom, then start darting around randomly, then settle down again and die.
  2. Caitlin86Well Known MemberMember

    what r ur water parameters? can u get ur parameters tested at the lfs? Im thinking ur tank couldnt handle the bioload of the new fish which then caused ammonia spikes...stressing out the fish..lowering their immunity..introducing infection due 2 bad water quality.

  3. AllilangNew MemberMember

    i sad in my first post that i cannot test my water. I live in korea and there are no ways to test it here. Since i cannot test it, I do frequent water changes.

  4. -Mak-Fishlore VIPMember

    You are very overstocked, and the neons and mollies aren't temperature compatible. Try to reduce the temperature to 25 C just for now.
    Mollies need at least 29 gallons (110 liters) ideally.

    I'm thinking stress coupled with ammonia poisoning was the cause of death.

  5. KiksWell Known MemberMember

    I agree with -Mak-
    Some of your fish aren't compatible, some of your fish aren't suited for a 16 gallon tank, you're extremely overstocked and some of your fish need to be in bigger schools.

    You need to get rid of some of the fish if you want your fish to live a comfortable life that's longer than a couple of months. Also, the symptoms you're describing sounds like ammonia poisoning.
  6. AllilangNew MemberMember

    Thanks for responding, but I have been very careful. The mollies and tetras have similar water temperature tolerances, and the tetras are completely unfazed by the event. I have live plants for nitrogen and do frequent water changes while I wait for the good bacteria to build up. I always make sure to put the water in a bucket for 2-3 days for the chlorine to dissipate. The fish were all very healthy for 2 weeks before the sudden mass death event.

    I know that mollies and guppies are actually the same species since they can interbreed. That also means they can catch the same diseases. The neon tetras and cory cats are unaffected and totally different species so they may be immune to a viral agent.

    My tetra/barb tank is more overstocked than my guppy tank while I wait for their new big tank to arrive, and they are completely fine.
  7. el337Fishlore LegendMember

    If I were in your situation and couldn't test my water, I'd keep a VERY lightly stocked tank. Rehome all but the neons and corys (what kind are they?) as I agree you're extremely overstocked.
  8. KiksWell Known MemberMember

    The thing is just that you don't actually know how your fish are doing, cause you can't test the water. Plenty of fish look just fine without being fine. I don't think your fish are fine at all, since they're dying. No matter what you do your fish don't have enough space. Some of your fish need way more space and you have a very crowded tank. You can't fix that issue unless you stop overstocking or buy a bigger tank.

    Oh, and one more thing. You wrote "I have live plants for nitrogen and do frequent water changes while I wait for the good bacteria to build up."
    Does this mean that you have all these fish in a tank that is not cycled?
    Last edited: Apr 22, 2017
  9. AllilangNew MemberMember

    Everyone saying it's overcrowded and to rehome them... remember that half are dead. The numbers I gave were from before the deaths.

    Most mollys and guppies are dead. I dont judge health by 'not dying'. I do so by activity and appetite. The day before the new mollies and the mass death, they were very active and hungry. The next day, they stopped eating and fell sick and started dying within hours.

    I think Nitrate issues would be more gradual. Not so sudden and catastrophic. After the 8 hour long death festival why would they suddenly stop dying if the nitrates were still present?
  10. el337Fishlore LegendMember

    The fact that there are fish dying does mean your tank isn't healthy and is most likely not cycled. But you'll never be able to rule out water quality if you can't test your tank either. Ammonia/nitrite/nitrate buildup most likely got to a toxic level due to the bioload your biofilter couldn't handle which is why you started seeing deaths later on. What fish do you have remaining ?

    And where did you buy these fish? If it's from an LFS, do they not sell testing supplies or maybe you could ask them how to source one?
  11. AllilangNew MemberMember

    I appreciate the feedback. Right now there are about

    2 molly
    3 guppy
    5-6 platy
    3 neon tetra
    3 cory cat

    All are very small breeds. The mollys are the biggest and only 1 inch long. I got them from the department store. I tried to find testing kits there, but no luck. No pure pet stores in the area carry fish.
  12. KiksWell Known MemberMember

    You're still overstocked in my opinion and as El337 says, if I were you and couldn't test my water I'd stock very lightly to try to prevent these issues. The neons should still be a bigger school and the mollys don't belong in a 16 gallon no matter what. Sorry.
  13. el337Fishlore LegendMember

    It's not really the size they are currently that matters but the adult size they can potentially get to. Aside from the size though, it's the bioload that is the concern. The mollies, guppies and platies are very high bioload fish. If it's not possible for you to upgrade to at least a 29g, I would rehome them. Then up your neons and corys to 6 each.

    Could you look online for a testing kit? I'm not sure what's available in Korea.
  14. BReefer97Well Known MemberMember

    The bioload in the tank is far too much. Especially if you can't check the water. The new fish you put in added to the ammonia produced, probably shocking the other fish. I would do a water change and I wouldn't add anymore fish.
  15. OnTheFlyWell Known MemberMember

    I don't think you are extremely overstocked if you had good water. If you knew you had a good water source a small water change every few days would probably make it manageable. Most livebearers are a little dirtier than other fish. Eventually you will have a problem as fish grow. A few more may die and solve that problem for you. You do need to mail order a liquid test kit when you can. Korea is a modern nation. You can get a kit if you can afford it. My daughter was born in South Korea. She would not be happy if I don't try to help you. :)
  16. -Mak-Fishlore VIPMember

    Even with frequent water changes I do believe you are still overstocked, especially if the tank is not cycled, and you have no way of knowing if it is or isn't. Try to find a liquid test kit online.

    You should not wait until more fish die to solve the problem.

    Mollies prefer upper 70s to low 80s, neons like low 70s.

    Letting the bucket sit out will allow chlorine to evaporate, but chloramine will break down into ammonia as well. I don't know if your water has chloramine in it, but it's becoming more and more common.

    Mollies and guppies are not the same species. One is Poecilia sphenops, and the other is Poecilia reticulate. Same genus, yes, and they may interbreed, though I'm pretty sure offspring are sterile.

    It is extremely hard to tell if fish are "fine". I've kept fish in awful conditions before I knew better and they were active and eating up until they died.
  17. FahnFishlore VIPMember

    You can't judge a fish's size based on what you buy from the store... an adult female molly can be over 5 inches. Your tank, even after all the deaths, is still very overcrowded and I suspect the cause of death was bad water quality from too many fish in too small a tank.
  18. AllilangNew MemberMember

    Thanks for your replies,

    @Fahn I know that fish grow, but the small fish should have had less of a bio impact on my tank than full sized fish so I am surprised that everyone thinks its an ammonia problem.

    I went to check on them Saturday and no one was dead, but still sluggish and little appetite. On Monday, the male molly, baby and a guppy were dead. All guppies, platys and the molly seem lethargic either staying at the top or bottom. Their appetite has not improved. I fed them half of my previous dose, and that was allowed to settle on the bottom. The only fish seemingly unaffected are the neon tetras and cory cats. Neons school around the middle, and the cory cats scavenge at the bottom like normal. I did a partial water change again today and I hope the situation will improve in the next few hours.

    I bought a water test kit online (so expensive) It is an american import so I should be able to do it just fine. My Korean isn't good enough for scientific stuffㅠㅠ

    My semi-aggressive tank has had no where near the problems of this tank even though it is more overstocked due to its size. Their new 16 gallon tank should arrive today, and I should be able to transfer them tomorrow. I plan on transferring the filter and gravel too, so it should help jump start the nitrate cycle.

    Other than size, the small tank also has a submerged filter while the guppy tank has a sponge air pump filter. Could the agitation from the submerged filter be helping dissipate the nitrates?
  19. AllilangNew MemberMember

    The mass deaths are over. I never lost any neon tetras, platys or cory cats. however, the guppies still seem to be not doing well. First the females started sitting on this flat topped rock in the tank. sometimes the males would rest on their too or swim around. I just vacuumed the gravel and changed some water and found every single guppy sitting on the rock.

    When the fish died before, they would sit on the gravel and not respond to tapping on the glass very much. These guys respond, but just go back and sit on their rock again. They will even swim around to get a better seat.

    The test kit should arrive today, but even if it shows bad numbers, I am not sure what I can do. I can find anti-chlorine and bacteria boosting treatments, but nothing to get rid of nitrates.

  20. pixelhootValued MemberMember

    Hey! Just wanted to peek in. Been a guppy owner for quite some time.
    Really, it does make sense logically to think that since fish are smaller, naturally their waste output would be smaller. While this is true in the idea that a little Guppy would not have the same bioload as a massive Arowana, it is not true if you shrink the fish down to a Tetra and still tried to compare it to the Guppy. Guppies, while we love them, are very messy fish. To put things bluntly, they are messy eaters and poop a lot. This causes your bioload to be significantly more increased than if you had the same amount of Tetras, hence why everyone is suggesting you stay with the Tetras over the Guppies.
    Now this idea applies to Mollies and Platies as well. While you may not have known it at a glance, all these really poopy fish being together causes the Ammonia levels to spike, and thus causing stress. It would be as though you were living with your own waste everywhere and breathing in the smells and seeing the sights.
    From what I can tell, the fish still appear to be stressed, and it would be a good idea to start taking action to remove some of the fish (and, by extension, the poop). The people who have posted before have given some nice advice on what you can keep and what has to go. I hope I helped illustrate how some little fish can have a bigger bioload and what you can do about it!

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