Help-fish are dying

Magenta

I have had my community tank for 2 years now. I keep guppies, tetras and platys.
I bought some new Guppies and Black Neons last Wednesday and ever since my fish have all been dying. I've lost about 5 or 6 in the past week and I have a Cardinal Tetra and one of the new Guppies lying on their sides on the bottom of the tank right now. These are the first 2 I've seen showing any signs of illness, I found the rest already dead. It's like they're just dropping dead.
Does anyone have any idea what causes sudden death like this? I'm so disappointed. The fish are dropping like flies.
They are on the same cleaning, feeding etc routine as always. It's just since I got the new fish last week it's started happening. It must be a disease if it's affecting my old fish too.

Pimp Ninja

This is going to be a lot of questions for you.

Are the new fish dying, or is it just the old fish?
Is it a mixture of both new and old fish dying ?
Did you quarintine the new fish before adding them to your tank ?
How big is the tank ?
How many fish were in it ?
How many fish were added ?
Are the sick fish showing any signs of illness (flicking/gasping at the surface/spots/redness etc) ?
Do you have any test kits (ammonia/nitrite/nitrate) to check the water quality ?

Im thinking of two possible causes off the bat
1. The new fish had an illness which may have spread to the tank.
2. The filter bacteria were not able to cope with the additional biological load with the new fish and there may be a build up of ammonia in the water.


If its an illness, we will need to look for identifiers to advise appropriate treatment.
If it is ammonia build up water changes should help.

Magenta

Pimp Ninja wrote: »

This is going to be a lot of questions for you.

Are the new fish dying, or is it just the old fish?
Is it a mixture of both new and old fish dying ?
Did you quarintine the new fish before adding them to your tank ?
How big is the tank ?
How many fish were in it ?
How many fish were added ?
Are the sick fish showing any signs of illness (flicking/gasping at the surface/spots/redness etc) ?
Do you have any test kits (ammonia/nitrite/nitrate) to check the water quality ?

It's a mix of new and old.
No, I never usually do and there's usually no problems. I just float the bag for 20 mins and then add in the fish. I don't have a second tank just for quarantining.
Tank is 90L.
There were about 15 fish in it, all about an inch long.
No symptoms at all.
No I lent my kits to a friend and now he's moved house and can't find them.

Pimp Ninja

How many fish were added?
- Im thinking its most likely an ammonia build up then.

The new fish, combined with existing are producing more waste than the filter is used to deal with.
The bacteria in the filter need to multiply sufficiently in order to break down the new levels of ammonia in the water.

Get an ammonia test kit if you can, in the mean time do a mininum of 10% water changes daily to try and keep ammonia build up down untill your filter bacteria have multiplied sufficiently to cope with the new bio-load.

lrushe

If the fish are showing no symptoms I would suspect the water quality being the problem. Try doing a water change and hold off adding anymore fish until the water quality settles down. I had this problem alot in the begining when I first kept fish as I could never stop myself from buying too many fish at once, I've learnt better now and never add anymore than 2 fish a week