shibunkin fish died

Question
Hi there, i have a 500 ltr tank just recently purchased, i run two filters both with carbon filters in them, the tank has been set up for 3 weeks now.  it had 6 fish in it, 1 small blue fantail, 2 small gold fantail, 1 small shibunkin fantail, 1 small blackmore, and 1 very large shibunkin (3 years old).  I had two fish to begin with which were the large shibunkin and a small gold fantail which lived in a much smaller tank.  All was going well, with the new tank, i introduced two new fish at a time after quarantine in another tank for several days.  Yesterday morning i noticed the large fish not eating and by the time i got home she was dead.  She, who we thought was a he, (name BIG AL) appeared to be laying eggs everywhere two days prior to her demise.  Can this event have been too much for her like some fish after spawning can die?  I would hate to think that we have done something to kill her inadvertently.  The other fish are all as good as gold (excuse the pun).  regards Sharon

Answer
Hi Sharon,

There are a couple of notable issues here.  First, you should never, ever keep larger single tailed goldfish like comets and shubunkins with fancy goldfish like fantails.  Eventually the single tails will get much larger and aggressive with the fancies and will bully, if not kill them, and will also out compete them for food.  Single tailed fish also need more like a 100+ gallon (380 L) for themselves but a pond is best because they get so large.  Many people believe if they keep them in a smaller tank then they will just grow to the size of the tank.  Not true!  The outside of the fish indeed stops growing because there is nowhere to go but the insides continue to grow to capacity until the fish dies from organ failure.  And while you have a nice 132 gallon (500 L) tank, it's not going to work with a single-tail & fancy goldfish mix.

Also, if the tank has only been set up for 3 week was it cycled prior to adding the fish?  If not the shubunkin may have been the 1st of many deaths to come.  All newly set up tanks go through a nitrogen cycling process where the waste that the fish creates is broken down into ammonia, nitrites and nitrates.  You should ALWAYS have 0 ammonia, 0 nitrites and 5-20 ppm nitrates.  A cycling tank will kill fish because it's when then beneficial bacteria is building up to eat the waste and convert it but before the colony is sufficient the ammonia and nitrites in the tank rise and this causes stress, illness and finally death to fish.  It's always recommended that you cycle before adding fish.  I would test your ammonia, nitrites and nitrates immediately.

If your water was fine it could have simply been stress.  I recently moved over all of my tropical stock from a 55 G tank to a 120 G and lost 7 fish that week, more than I have lost in years and years combined.  It was simply the stress of the move as they had no outward appearance of disease or distress.

You can read more about the different classes of goldfish and the nitrogen cycle at:

www.aquariumfish.net

Good luck : ) April M.