My Fish..lots of Questions!!

Question
Dear Linda,
  Okay I have a lot of questions. First of all,I had 6 fish who unfortunatley recently died, of unknown causes, and that is why I am writing to you!. Well,I had neon zebra danios and the first one died of what my dad thinks was an aggressive fight. (he was missing an eye and was missing or  had severely damaged fins)the other fish had what looked like clear slimy stuff filled with bubbles(?) around their fins.I also had a halfmoon beta that was navy blue. Soon it started turning a metallic silver-gray color, and froze a lot in the water, and also had milky-white eyes before it died. The other neon zebra danios died over night ad when in woke up, the were belly up in the water. These fish also hung out at the top of the water for the time before they died. Thank you! hope you can verify why my fish died! Also if it's possible give me some advice on fish. (i might get more)
  Sincerely
     Ariane D. AGE 12

Answer
Hi Ariane,
The first thing to do is to check your water for ammonia, nitrites, and nitrates.  This is the most important thing to do.  Your ammonia level should be zero, your nitrites, zero, and nitrates must be low.  You can buy these small test kits at the pet store, and they are very handy to have.  They should be number one in your fish cabinet.  Never add a fish if you have ammonia, or nitrite and nitrates in your water.  Once you water chemistry is good, do not add all the fish at once.  You didn't mention the size of your tank, but usually it is one fish every 5 days.  Adding too many fish, or overstocking a tank will change the water chemistry, disease happens, oxygen is low, and the fish die.  When keeping danios, and other fish, you need a filter so that there is water movement in the water.  When there is no water movement, or not enough, fish die of lack of oxygen.  I think you problem is ammonia, or nitrites in your water.  You have to let your water cycle.  Cycling a tank means that it must run with nothing in it for a few weeks until your water chemistry is perfect.  Always buy fish that are compatible...not all fish get along.
Once your water chemistry is right, you must do 25% water changes every week to keep your water clean, and free of decaying food, and fish waste.
I hope this helps
Lynda

Hi Ariane,
Now that I know the size of your tank, I also know the reason why your fish are dying.  A 2 gallon tank is not big enough to have fish in it.  These tanks are used for hospital tanks.  When a fish gets sick, we use a little tank to try and get them well again.  Fish need room to swim.  You should consider buying a bigger tank so that your fish will be happy.  Fish kept in small tanks do get stressed, and stress causes sickness.  No fish can survive in such little space.  This is the main reason that your fish died.  I'm sorry, but had to let you know.
Lynda