Urgent Help, fish dying!

Hello,

I’m new to this forum and have a tank emergency with fish dieing rapidly.

Not sure what the problem is??

Had tank for about 6 months, but is second hand, approx 240 litres. Fish have been fine until I did a half tank water change about a week ago.

After water change, a couple of rummy nose tetras lost their red colour, but otherwise seemed ok until 2 days ago, one died. I checked water conditions were fine and double checked at local aquarium shop.

Did another water change as others started looking sick and breathing fast. Woke up this morning and a Congo tetra and 2 ghost catfish were dead and other Congo tetras has reddish marks in places in scales and fins tattered.

Got home tonight and 2 more Congo’s, 5 neon tetras, and last 3 rummy nose tetras dead.

remaining fish all breathing rapidly and look unwell. One Congo going from swimming normal, to flipping around and upside down.

Not sure what to do? No shops open. Have had white spot before and doesn’t look like that?

Hi and welcome to the forum

Did you dechlorinate the new water before adding it to the tank?

If fish act funny straight after a water change, they have usually been poisoned by something in the new water, or the container used to carry the new water to the tank.

In summer the water companies sometimes increase the chlorine levels if the weather is going to be hot, or if they do work on the pipes. They don't tell customers that but it does happen.

Your best bet is to use a basic dechlorinator like Wardleys Tri Start and double dose it in summer or during hot weather. And make the water up at least 30 minutes (preferably 24 hours) before using it.

You should also check with the water company to make sure they haven't started using chloramine instead of chlorine.

If you are filling the tank with a garden hose, make sure you run water through the hose for a few minutes before using it to fill the tank. Garden hoses have a chemical in them to help keep them soft and supple and stop them kinking. In hot weather the hose leeches this chemical into the water and it can poison fish, birds, animals and peoples.

Black poly pipe (irrigation hose) does not have this chemical in and is a safer option than a normal garden hose.

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About the best you can do now is increase aeration/ surface turbulence to maximise the oxygen levels in the water.

If you have some carbon (black granules for the filter), then put that in the filter to help remove chemicals that might have gotten into the tank.