fish gasping for air

i done a water change this morning and fed my fish, about an hour later they were all gasping for air and three died (tetras), i was looking it up and it may have been a lack of oxygen from too much amonia in the water so i did a 50% water change with and 4 hours later did another 25% water change the fish seemed to calm down a bit, but now 4 hours later they are back on top of the tank gasping again, i was looking it up and maybe i have nitrates from over feeding? Any advice would be great thanks

2 possibilities come to mind.....(1) You didnt use dechlorinator in the fresh water you added.... (2)the tank is either not cycled yet (if its a new setup) or gone into a mini cycle (if its a well established setup).....Could you answer the following questions so i can get a bit more info from ya to help you solve your problem....

How long is the tank set up?

How big is the tank (in litres)?

What kind and how many fish are in the tank?

Also have you tested for Ammonia,NitrItes and NitrAtes?

There could be a number of problems here.
Here are some immediate chemical reasons:
-Lack of oxygen......so increase aeration, and the new water should have been well aerated.
-Ammonia would also make a fish gasp....and you may also see neurological problems such as leaping about madly.
-Carbon dioxide is not a likely problem as that would tend to make fish go to the bottom.
-Did you dechlorinate correctly?
-You could have churned up Methane or Hydrogen Sulphide or other toxic gas when doing the water change.
-Plus...more.

There is also the potential that dead gunge has been spewed from the filter system if it were powered down or partially cleaned.

OR, the water change may have churned up some rotten food and fish ate it (death from fungal toxins is quite common and very rapid)

Then there are the physiological disturbances:
-the pH could have changed so rapidly that the fish were unable to rid themselves of ammonia (that would be my first port of call);
-the rapid change in nitrate levels could mean that the fish is unable to re-establish itself;
-other sudden changes (including temperature) will mean that the fish cannot cope.

In general, stress will affect the kidney and the general functions in a fish.....ammonia build up can be result of that (and it is no use doing an ammonia test as it is the body of the fish).

As for a solution....it depends on the damage already done.
I would instantly add Tetra AquaSafe (as it contains vitamin B1) and then add ammonia adsorbing and nitrate adsorbing zeolites (do not add something Amquel as that saps up oxygen).

I would advise review the water changing techniques.

Ian

Thanks guys for your help, i woke up this morning and there was another tetra dead, so i brought a sample of the water to the pet shop and the ph level in my tank was really low, he recommended some coral sand in a tight in the filter and it seems to have fixed the problem, thank god.

In a few weeks i'm going to replace my stones with all coral sand to keep the ph up. i live in a low ph area, hopefully this will help others aswell.

Low PH the Rolls Royce of complaints....

Glad to see the issue is now resolved, but can I suggest two small things:-

- A good test kit, used on a regular basis will help identify problems and it something you can easily do yourself; and,

- Water changes in the future - you might need to look at conditioning your fresh water to bring the ph up so that it is not a shock to the fish when making water changes.

Brian

What is the PH straight out of your Tap?

Kev.

When you say 'low pH' what exactly was the pH?

Do as Stretnik asked....test your source water. and do a hardness test.

It may well be that your pH was unstable rather than just being 'low'. ie having little pH buffering.
If your water was quite soft and acid then it is exactly the type of water that is often unstable....and you get mad transient pH swings. Those swings will not just kill a fish directly by physical damage, but they will also make it difficult for a fish to rid itself of waste products and will affect gill function.

Ian