My friend has a 3ft community tank and a couple of weeks ago there was an enormous bang and her heater exploded. She cleaned up the heater, replaced it straight away and did a 50% water change. Since then the tank has just gone downhill. She has been doing almost daily water changes (not 50% of course) but the water is constantly cloudy and the fish are dying daily. Someone suggested mercury poisoning. Is that possible? Does the heater have mercury in it? She doesn't have a spare tank and is at a loss about what to do. Any advice?

No, the heater does not have mercury in it, I also can't find evidence of nichrome wire(The heater wire) being related to chromium poisoning.

There is nothing toxic in the heater, there's some other reason her fish are dying.

Yeah I thought the mercury theory was a little odd too. I guess it is whatever is making the water cloudy.

I would think that it was the shock wave from the exploding heater that damaged internal organs in the fish.

We all know that kids shouldn't be knocking on the glass of the tanks because of that!

So if that would be the case then no water changes will help, as the damaged fish will just die over a couple of weeks if they cannot "repair" themselves.

Has she had the water tested at all?

Is she cleaning the filter every time she does a water change?

When the heater xploded had she done anything to the tank that day?

I cat say ive heard them actually explodin in the tank doesnt mean it cant happen though

Brad

Not 100% sure about this but I'm fairly sure fish are not as susceptible to mercury poisoning as humans. I believe fish have a mechanism for binding many heavy metals into their system without becoming toxic.

This is why it's bad to eat shark from the fish & chip shop as the accumulated mercury is much higher in the animals at the end of the food chain.

Maybe they are effected by high levels of heavy metals but a heater will not be the cause.

If the heaterstat had developed a small leak it is possible water got into it to cause it to explode.

Temp drop + 50% water change could've easily resulted in the death of some of the beneficial bacteria in the filter. Fish could simply be dying from a nitrite peak. First thing I'd do would be a nitrite and ammonia test.

Also they may have unplugged the filter as well when the heater was disconnected. Just another possibility.

I find the bacteria that does nitrite -> nitrate is the easiest to kill, and nitrite is a silent killer.

Carla wrote:

I would think that it was the shock wave from the exploding heater that damaged internal organs in the fish.

We all know that kids shouldn't be knocking on the glass of the tanks because of that!

I always thought "knocking" on the tank was bad because it frightened the fish. Are you saying that it could actually cause a shock wave and kill the fish???

Caper

Yes it can.

It damages the internal organs including the swimbladder.

So if there was a loud "Bang" that everybody could hear in the lounge - I am sure that the poor fish would have had internal damages too.

Unfortunately it seems that most people look for chemical problems first, but fish are very susceptible to sound waves, which seems not to be taken into account.

Remember how people used to fish in Sout America, Greece and Asia - with explosives. The fish would just float onto the surface - still alive, but damaged - and people would pick the ones off that they either wanted to eat - or sell to the Aquarium Trade....

I have had a heater or 2 explode quite voilently before (they sprung leaks and water caused it) with no ill effects to the fish..

I would be going for something else possibly a bacterial bloom or filter die off for some reason.. Did the filter turn off for a long period when the heater exploded and the CB's or powerboard tripped out?