Parasites killed my fish - Tropical Fish Keeping - Aquarium fish care and resources
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post #1 of 21 Old 05-26-2013, 03:37 AM Thread Starter
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Parasites killed my fish

I had a tankful of fish, then a few days ago I noticed the all the fish had torn fins and started behaving strangely. They all started to sit at the bottom of the tank and looked really weird. They all soon died and I couldnt make out what was wrong, as the water was changed a couple of weeks previously and the fish seemed so healthy. Some of the fishes were not less than 3 years old. Upon emptying the tank I notice very tiny parasitic worms in their millions on tank accessories! That is what killed the fish. I would like to know how did this happen, where did these worm/parasites come from and how should I deal with it next time it happens?
Thank you for any help and advices.
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post #2 of 21 Old 05-26-2013, 04:10 AM
Hi, junglebee. I'm checking out your thread as you asked. :)

First, I know what those little worm things are and it'll be surprising but they DID not cause the death of your fish. Those nasty little bugs are called planaria and they exist in lots of tanks and they are harmless. Most of the time, their numbers are so low that we never notice them but sometimes the tank conditions are just right and they have a population boom. This could be from over feeding or from not changing the water often enough.

What size is your tank and how often do you change the water? This could be the key to us figuring out what caused the death of your fish.
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post #3 of 21 Old 05-26-2013, 06:02 AM Thread Starter
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Thank you for your reply :) Its a three-foot tank that had different types of fish and some goldfish too. I clean the tank about every 3 months. The fish were perfect for a few weeks after I cleaned it and then suddenly they started getting sick. My fish were always greedy so I did feed them abit extra. Oh also, Ive got a plecostomus thats three years old and is still sick. I dont know how to treat it, it looks 'blind'.. any advice is most welcome.
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post #4 of 21 Old 05-26-2013, 11:22 AM
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Now we need some more data please. Have you ever tested the tank water for ammonia, nitrite and nitrate? And pH?

And just so we are all clear, you are not doing any regular (weekly or whatever) partial water changes other than the "cleaning" every three months? And this cleaning is completely emptying the tank of water and refilling? Are you cleaning the filter?

Exactly what additives are going into the tank water? Conditioner (which one), salt, etc.?


Byron Hosking, BMus, MA
Vancouver, BC, Canada

The aquarist is one who must learn the ways of the biologist, the chemist, and the veterinarian. [unknown source]

Something we all need to remember: The fish you've acquired was quite happy not being owned by you, minding its own business. If you’re going to take it under your wing then you’re responsible for it. Every aspect of its life is under your control, from water quality and temperature to swimming space. [Nathan Hill in PFK]

Last edited by Byron; 05-26-2013 at 11:25 AM.
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post #5 of 21 Old 05-26-2013, 04:45 PM
Junglebee, feeding the extra bit is probably what helped to create the planaria bloom. Would you mind telling me how many fish you have in the tank? Also, I'm glad you were able to get your avatar to show up. Did you resize it like I suggested?

Just based on the info you've given, I think your fish may have gotten sick because the water quality isn't very good. If you aren't changing the water very often and you're overfeeding, you're creating a lot of pollutants that will make the fish sick, pollutants like nitrate and ammonia and nitrite. It's important to try and do a partial water change as often as you can. When the water quality isn't very good, fish become stressed and their immune system crashes.

Please let me know the number of fish and how often you change the water on a regular basis, okay?
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post #6 of 21 Old 05-27-2013, 06:40 AM Thread Starter
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@Byron, thats true. I only completely changed the water about every three months. My fish always thrived. I only use aquaSafe. No I never tested my water. Any advice I would appreciate.

I had around 20 fish, common ones, tetras, and some goldfish. Its an underground filter so I can only clean the whole tank at once. The water was very clean when all the fish died. I only have a 6 inch plecostomus left and I desperately seek help in treating it. It looks 'blind' in the eyed and needs treatment. But Im not sure what to do. Any advice please.
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post #7 of 21 Old 05-27-2013, 06:46 AM Thread Starter
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@Sakura, yes my avatar has had to do with the sizing! Thanks I got it right. Im loving this forum, right from the first day I find it very helpful thank you again!

Oh and my fish were really eager to eat so every so often I just fed them a little, and of course the pleco was there to eat as he is a big fish too. So after about two weeks of clean water the fish died.
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post #8 of 21 Old 05-27-2013, 07:12 AM
Hi Junglebee. I'm sorry to hear you lost so many fish. It sounds like your pleco may have cloudy eye because of the poor water quality. Clean water will really help with that. The cloudy eye may not ever go away now but the clean water will keep it from getting worse. If you want to treat it, you will most likely need to isolate it in a smaller tank but treating plecos can be difficult because they are sensitive to many medications.

Based on your tank size and filter, I would recommend you try to change at least 30% or more of the water once a week. I know this sounds like a lot but fish, especially goldfish, really put out a lot of invisible waste. You don't need to completely change all of the water. Once a week, using a gravel vacuum or siphon hose, suck out about 30% or more of the water and replace this water with clean water that has been treated with a good dechlorinator.

You may not want to add any new fish until you have gotten your tank fixed. Your tank will need some time to reestablish its filter bed.

I think what may have happened is when you changed all of the water, you removed all the good bacteria that was in the undergravel filter. This bacteria helps to convert toxic wastes into less toxic wastes. Without it, these wastes built up and made the fish pretty sick with ammonia poisoning. The only effective ways to control these toxic wastes is with this bacteria and with frequent water changes.

You may want to get a test kit that will test for these toxic wastes - ammonia, nitrite, and nitrate. That way you can monitor the levels and if they get too high, you'll know that you need to do a water change.
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Last edited by Sakura8; 05-27-2013 at 07:46 AM.
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post #9 of 21 Old 05-27-2013, 09:58 AM
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From what I have heard, the jury is still out on undergravel filters. There are some good articles on how to deal with them: I think keeping them from getting clogged is one issue.
Even with an undergravel, it is still advisable to to a weekly water change. 10% is a minimum, and more is always welcomed.
I don't think anyone has mentioned it, but mixing goldfish with tropical fish is not a good idea either. Goldfish are constantly eating and, I think, produce a great deal of waste. They also like different temps. Your tetras and other tropicals like it warmer, and goldfish on the cooler side. There are better answers than mine out there.
Buy an API (or similar) master test kit, liquid test kit, to determine your water parameters. This may help in monitoring spikes and aid in counter acting detrimental ones.
good luck
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post #10 of 21 Old 05-27-2013, 12:13 PM Thread Starter
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I want to thank all of you who gave excellent answers. I was really really sad when all my fish died, I love watching them for hours, and now I will start all over again. Ive noticed that a water tester is a must. With an undergravel filter all the dirt stays under, so if I change the water the dirt wont be coming out. Is that okay? And the way to go about treating my pleco is just clean water, am I right? He's the strong one thats why he is surviving still. But I feel so sorry for him because he was such an active fish, always ready to eat. Now he's in a tub while my tank gets settled.
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