fancy guppies

Question
hi!
im not sure if you can help, but im running out of ideas! ive got a 40 gallon tank with 2 pumps, and ive just cleaned about 1/3 of the water, twice this week to try and fix my problem. i have about 15 fancy guppies, and 2 of them are acting spastic. they swim in circles and upside down and sometimes they just chill on the bottom of the tank. but sometimes they seem fine... ??
im not sure what i can do to help them if its a disease, or if it will spread to the other guppies. any suggestions? thanks!

Answer
Hello Jai,
It is very hard for me to diagnose.  It could be a viral disease caused by water conditions,  transmitted from one fish to another while still in the Pet Store.  Have you checked your water for ammonia, and nitrates.  Fish will act this way if you have ammonia or nitrates in your water.  If you do, you will have to make water changes every day of 10% to get rid of it.  It could also be a lack of oxygen, so check that they are getting enough oxygen.  There should be lots of water movement in your water.  Never fill your aquarium to the top.  Leave a space so that the filter will splash water into your tank, making water movement.  I don't know what kind of filters you have as you did not mention this.  A forty gallon tank should have a 500 aqua clear filter, or the equivalent. A 300 aqua clear filter is good too, but don't overstock your tank. Check your water every week to make sure your water chemistry is good.  You can buy these small test kits at your pet store, and they should be number one in your fish cabinet.  Ammonia is the number one killer of fish.  Many diseases start with poor water conditions, so it is better to check it every week to make sure your water is okay.
What is surprising is that they are not always like this, and return to normal.  It doesn't sound good, so keep an eye on them, test your water, make sure it is okay,  and hopefully everything will fall into place.  I cannot tell you more, as I do not see the fish...I am guessing at what it might be.  If they are thin, it could be T.B.  observation is the key.  There are so many diseases, it is hard to pinpoint what those 2 fish have, especially that they have nothing on their bodies, no fungus, no ich...it could be something internal too.  If they keep swimming in circles, and your water chemistry is perfect, then I would put them to sleep.  The best way to do it, is to take a plastic bag like they have a the pet shop, fill it with a little water from your tank, and put your two fish in it.  Make sure that there is air in the bag...twist it, and tie it, and put it in your freezer.  This will put them out of their misery, and they will fall asleep.  
Hope this helps you in some way..
Lynda