My dads fresh water fish suddenly decided to commit mass suicide!

Question
QUESTION: Hi, my dad went overseas for a week and entrusted his fish to me. They live in a pond. He forgot to give me specific instructions, so I had to estimate the amount of anti chlorine and food to give them.

My dad's routine is to feed the fish and top up the pond in the morning (with anti chlorine) and top up again in the evenings (no anti chlorine) but I did it in the evenings only.

I put quarter capful of anti chlorine before filling up the pond (turns out its 1/2 capful) and 1 cube of frozen bloodworms (turns out my dad feeds them fish flakes and only the bloodworms once a week).

By the 2nd day, the fishes were dying one by one. I have no idea what happened. I do not know their breed, but they looked whitish with a little bit of black and yellow spots. Some of the dead ones were whitish and pale red as well.

And when I finally had to clear out the pond, I found a dead fish that got stuck in between some pond weeds and when I scooped it out, I realised its head was already half dangling off.

Is it some kind of disease that decided to wipe out the fishes or did I do something wrong? e.g feeding wrong food or not enough anti chlorine? Or is it because I did not do exactly what my dad did?

I asked a few fish loving friends and they said it shouldn't have made much of a difference, but I'm still not sure. Please advice what went wrong!

Thanks so much!

ANSWER: Pamela,

Since its a pond i will guess either gold fish or Koi. Without knowing what type of fish it is, this will be a bit tricky. So, I will see if I understand and i will try to figure out what happened. When you say top off the pond in the morning with anti chlorine, are you adding water to the pond as well? Did you not top off in the morning, but only at night with water and no anti chlorine?  The anti chlorine should have been added to the water before you filled up the pond. If i am understanding you right. You added anti chlorine to the pond water, then filled the pond up? You fed them bloodworms everyday for a week? I don't think that could have been the problem, but it might have contributed to it. It sounds to me that there was a water issue. Maybe the ammonia spiked up, or the adding of the anti chlorine straight to the pond and not mixed with water being added to the tank. It could have been the changing of the routine. I have a friend that has a pond and they changed up the routine one day and fish acted very strange. Yes, there could have been a problem in the pond before you took over the care. But for them to die that way, i will have to stick with a water problem. Can you test the water and get reading for me. Like ammonia, nitrates, nitrites? If you can, that would be great.

I will wait to hear from you and in the mean time i will check out a few things and we will see what happened.

---------- FOLLOW-UP ----------

QUESTION: Hi Jaymie,

Thanks so much for replying so fast!

Ok, this is what my dad does everyday.

1) Fill up a big watering can with water and add 1/2 capful anti chlorine, then pour into the pond. (morning)

2) Feed dry food, they are tiny round little bits of food.

3) Top up the water in the evening, but no anti chlorine added.

And this is what I did...

1) Fill up the watering can with water but added only 1/4 capful of the anti chlorine, as he forgot to tell me the amt to add. (evening)

2) Feed frozen bloodworms.

I didn't do it in the morning as I have to rush off to work. Is that the reason why they acted strange?

The pond is an indoor pond, and the fishes aren't koi or goldfish.. I do not know the type.

They look something like this: http://www.dkimages.com/discover/previews/866/90009419.JPG but the black and yellow colourings are on the body and not on the tail.

Also, there is a thin layer of oil on the surface of the pond, despite changing the dirty fish water. Is it because I did not add enough anti chlorine and water?

Thanks so much for your help!

Answer
Pamela,

Ok, Here's the thing. Every time you add water to any aquarium or pond, anti chlorine has to be added. So, if water is added in the morning, then the anti chlorine goes in. When topping off in the evening, again anti chlorine has to be added. So, I am thinking that when the water was added, there was not enough anti chlorine added. I think you are saying that you did not top off the water in the morning. That in itself would not have caused a problem.

 As for the fish with the head dangling, that fish could have been dead already, before your dad left. That would mean that something was going on in that pond before you took over.

So, what i think happened was the water was added to the pond, but the amount of anti chlorine was not enough. By the second day, they were missing a full dose of the anti chlorine, so that is why they started dying.

Also, the bloodworms being fed everyday was not the norm for them so this could have contributed to the already existing problem.

As for the layer of oil. How did you clean the pond? If its cleaned by means of a brush, then the bad bacteria was reintroduced into the pond leaving the film you are seeing. One way to get rid of that is to do a 30% water change. That means remove 30% of the water in the pond and replace it with clean anti chlorinated water. I am assuming that all the fish are dead. If not, remove the living fish and place them in a different container with fresh conditioned water and an air stone.

I hope this help. I am here if you need any more help.