New Aquarium - Fish Dying!

Question
Hi Ron,

No, I didn't wash the tank with any detergent. The only thing I can think of is that on the first time I was a little too keen and fed them three times.. but this was just a small pinch of food each time. I haven't fed them today.
My other silver Dollar just died!
The water is a little cloudy.
One of the Leopard Angelfish ( the drunk one) is now swimming with his head pointing upwards.
No injuries visible on any of the fish, either.
The bubbles are just caussed by the filter pouring water back into the tank, I will get an airpump anyway.
Thanks,
Fiona

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The text above is a follow-up to ...

-----Question-----
Hi,
I've read a lot of information on this site, and it has been VERY helpful. I have added fish to my new aquarium - after having it fishless for around five days - two silver Dollars and two Leopard angelfish. The first day everything seemed fine. But by the next morning one of the silver dollars was swimming upside down, gasping. By that night, it had dyed. The next morning, the other silver dollar was staying close to the bottom of the tank and gasping for air.
I went to the local aquarium centre with a water sample and the boy just shurgged his shoulders and said to keep doing 20-25% water changes daily. He tested the PH levels and Ammonia levels and said everything seemed ok. Today, my other silver dollar is floating upside down and barely breathing, one of the Angelfish seems drunk, bumping into stuff and floating upside down occasionally and the other angelfish 'seems' fine. but they are both gasping.
From what I have read, I'm gathering this is all part of the Nitrogen cycle??? The toxins in the water are making them sick?
The tank is 38 litre (I think thats 10 gal?)The temp is 26-27 degrees celcius, I don't have an air pump but the filter is like a waterfall into the tank, so this is creating small bubbles.
I want to at least try to save ONE of these fish!!
Thanks in advance,
Fiona
Sydney, Australia.
-----Answer-----
Hi Fiona,
 Hmmm... something isn't right.  Unless you poured half a can of fish food into that tank there can't be enough nitrogen buildup in two days to cause that reaction.  

 By any chance did you clean the tank with any kind of cleaning agent (soap, disinfectant, etc).  Those can be extremely toxic to fish.   

 When you say "small bubbles" do you mean a few small bubbles or hundreds of bubbles?  You need hundreds and hundreds of bubbles of air in there.  Getting an air pump is generally a good idea by the way.   

 Also, are there any wound marks on any of the fish, e.g., missing scales?

-- Ron
  rcoleman@cichlidresearch.com
  Cichlid Research Home Page <http://cichlidresearch.com>

Answer
Hi Fiona,
 When you fed them three times, did they eat all the food?  You should only feed fish as much food as they eat right away.  Never put in food for them "to eat later".  It just rots and spoils the water.  

 Something still seems very peculiar to me...
you didn't put in any "natural" wood or rock or anything like that, right?

-- Ron
  rcoleman@cichlidresearch.com
  Cichlid Research Home Page <http://cichlidresearch.com>