chloe_y

Hi I am having a slight problem as we have one fish that seems to be causing the other fish to die. He appears to be in perfect health, but 5 other fish have died in his company. They were all goldfish, and apart from being dead there are no visible signs of why they have died. We moved the 'killer' fish to my friends tank and now two of her fish have died!
Please help as we are not sure what to do with him.

Mike19

what type of fish is the "killer fish"

Amanda

Well, if this is a 5 gal. tank you're talking about, it may be the size that's killing them. Goldies need a 20 gal. minimum for one, ten gal. for every fish after that.

Lucy

Hi welcome to Fish Lore

A little more information will help.
What kind of fish do you have and how many of each?
Do you know your readings for ammonia, nitrites and nitrates?
When was the last time you changed the water?

I agree an over crowded tanks can cause aggression but so can water problems.

chloe_y

I might have got the tank size wrong as its quite a big tank- although there has only ever been 3 fish in at a time. The goldfish are normal comet goldfish. We checked the ammonia levels as someone suggested that could be the problem but they were fine. We change around a 5th of the water every week and have been vigilant in keeping the tank clean to try and stop this problem. We also live on a farm and dont use town water- therefore there should be no chemicals in the water.

thanks

agabr123

do you know the exact reading for ammonia?

chloe_y

No im not sure sorry. I wasnt the one who did it

agabr123

okay, i think right now there are a few things that you can do...

1. buy a test kit, they are a little expensive in store ($30) but you can buy them online ($18 + shipping at petmountain.com), oh, and i'm talking about the API freshwater master test kit, so that you can do your own readings. if you are getting the LFS to test your water, they are probably just using strips which are very inaccurate.

2. get the measurements of the tank, most tanks sizes are pretty standard, and if you have the measurements it will be pretty easy to tell what you have

3. you should buy Prime for water changes, it detoxifies ammonia, heavy metals, chlorine, chloramine, even if you don't think you have any of this in your water, i say it's better to be safe than sorry

4. here is some info on the comet goldfish, i unfortunately am not very familiar with goldfish so the info you get here will be better than what i can tell you
http://www.petgoldfish.net/comet-goldfish.html

5. you're doing a great job with the weekly water changes, they are absolutely necessary and helpful. are you vacuuming the gravel as well? that is where a lot of waste will build up.

6. it says that you don't know about the nitrogen cycle, please read these links for the health of your fish!
http://www.fishlore.com/NitrogenCycle.htm
http://www.fishlore.com/Articles/TheNitrogenCycle.htm

Dozey

If you can provide the dimensions of your tank we can determine the size of the tank for you. (length x width x height) (inches or centimeters is fine)

To sort out why your fish are dying members are really going to need to know…
What fish are involved (a.k.a. the “killer fish”)
The water temperature
Accurate readings for ammonia, nitrites, and nitrates (An API master test kit is highly recommended)

Regardless of whether you are in the city or not you should be using a water conditioner for your water changes. Water conditioners not only deal with chemical used in city water but also other heavy metals. If you are using ground table water you are likely to have heavy metals in your tap water. Seachem Prime is an excellent water conditioner.

chloe_y

Thanks for all you help. Looks like i have a few jobs to do!

Also i still use a water conditioner