Shimmying Guppy

[jodhafish]

Hello everyone,
 
 
10 days ago I added 4 (all males) guppies to my 10 gallon tank (actual water volume about 7 gallons) after I had it fishlessly cycled.  All of the fish seemed to be doing well until yesterday when one of them (which happens to be the smallest in size) began swimming in the same spot.  After some searching, I discovered that this is known as shimmying and it's a symptom of stress due to water quality.  Throughout the last days, all my tests of ammonia and nitrite indicated zero levels (so my tank is indeed cycled).  On sunday, nitrate was about 20ppm so I did a 50% water change to bring down to about 10ppm.
 
Yesterday, when I noticed the guppy shimmying, I also tested the water and it had zero ammonia and nitrite and about 20ppm of nitrate.  I did another 50% water change, which brought the nitrate down to about 10ppm.  I also tested the ph after the water change and it was above 7.6 (the highest value in the normal ph range).
 
I feed the fish once daily in the morning.  I don't believe that I am overfeeding them because ammonia is staying at zero.
 
Does anyone have any ideas as to what can be causing this problem?  
 
One thing I can think of is that I never changed the cartridge of my filter since I got the tank which was 2 months ago, should I be changing it at this time to improve water quality?  also, since i introduced all of them to the tank, I began noticing that he was a loner a lot of the time (the other three seem to be swimming together in the same area, while he was always somewhere else).
 
all replies are much appreciated.
 
thanks
 
 

 

[PrairieSunflower]

Nitrate at 20 is a perfectly decent reading and you do not need to change the water to lower it.
 
You do not need to change the cartridge in your filter, that is where the good bacteria is housed that keeps your tank cycled.  If there is a build up of gunk in the filter, then you can rinse your cartridge in a container of old tank water (tap water can kill the good bacteria) and put it back in the filter.
 
I would think if your readings are all normal, 0,0,20, then it is more likely due to illness and not water quality.  What is your water temperature?
 
Are there any other symptoms?  Far as I know, the shimmies is a symptom and not a specific illness.

 

[jodhafish]

Thanks for your reply.  The temperature was around 80, I have since raised it to 82 having read that higher temperature can help with shimmies.  I also added some salt last night to increase the hardness of the water as low hardness was also cited as a cause for shimmies.  There are no other symptoms at this time.  He ate fine this morning and it looks like he's doing it a little less than before -- he's swimming around, then he'll stop for a bit to do the shimmying and then swim again, while before he would stay in the same place for a very long time.