Fishy postmortem. Advice required please

[OrmIrian]

We've been away for a week and paid neighbours teenage son to take care of of 5 fish, 2 rats and a cat. Cat and rats fine on our return but 2 of the fish were dead. One was 18m old and the biggest and healthiest of them all, the other was new at Christmas and seemed fine. No signs of anything wrong at all. When I hauled them out of the tank on Saturday they seem to have been stripped of their scales and their fins were all ragged. I suspect that was due to cannabilism. Is that likely? Fish sitter insisted they were alive and well on sat morning but they stank to high heaven so I am a little doubtful .

What could this be? I am worried about scale rot (or whatever it's called) but couldn't tell from the bodies if that was what happened. The tank was full of food - we're very careful not to overfeed and only feed once or twice a week but I don't know if overfeeding could actually kill a fish this quickly. I know it's probably a bit daft to worry but I don't want to replace the ones that died if there is something wrong with the set up or some infection in the tank and the new ones keel over! DD was distraught and even wrote them a little epitaph (Oh loyal fish! )

Oh dear, not what you need on a return from holiday. It sounds like overfeeding is the most likely cause of death to me - they were clearly fine when you left.

One of our fish died recently, and his fins went all raggedy when he fell ill. It was white spot (caught from a new fish introduced to the tank) so I think that fins can be a general indicator of health as well as a specific disease.(We cured the white spot but he was so weak he died anyway)

If I were you, I would completely change the water / sterilise the gravel before you restock, because if the dead fish had been in there for a while, there is probably some undesirable bacteria in there that could affect your new fish. We are going to do that following the loss of ours. Good luck!

For future reference you can buy feeders which dispense enough food for 3 or 7 days so you can leave them happily.
Sorry about the loss.

Thanks.

nab - I have some 7 day feeder things but completely forgot to put it in before we left. Frantic phone conversations with mate to go round and ask teenage lad to feed fish too.

neverending - I have been inspecting the oldest remaining fish and her fins do look a bit ragged but she is a fantail so I'm not sure if it's normal or not and I can't remember exactly what they were like before. We did buy a new fish but it was about 3 weeks ago and it looks fine. Will clean tank today and keep an eye.

The problem is that the bodies will rapidly deteriorate especially with 'help' from tank mates so it is difficult for you to tell if scale/fin rot etc was a problem.
If I were you I would clean the tank well -fairly large water change, and then watch the survivors carefully for a few weeks before adding new fish.

For over feeding to cause this I would have thought that there would be more obvious signs in the tank too - possibly algal bloom, cloudy water etc. Have you tested the water quality at all to check nitrite levels etc?

Thanks fangzooki,

I did a total water change yesterday, scrubbed the tank and all the ornament thingys plus all the bits of the pump I could get at, and sterlised the gravel. Fish back and looking OK. So far.DD wants to replace them straight away but I will wait and see.

Did you leave in the filter sponges? Cos if you didn't - with all that you may well end up with 'new tank' syndrome - ie you will have stripped all the good bacteria out that help to process the waste products.
If you have some 'Cycle' - you should probably add some of that to help. Our local fish place does chilled doses of bacteria in pots - no idea if they work as haven't tried them but might be worth a shot.

Sometimes a new fish can bring in disease that it may not succumb to itself. Perhaps that was the source, though from what you say I suspect the cause is overfeeding and fermenting food causing it. A complete water change and water conditioner added to it should hopefully be all that is needed. I'd watch the others for a month or so before adding new fish in, and make sure where you get them from quarantines them for a period before selling them on.

Yes - overfeeding. The excess feed pollutes the water. Fish need the clean water to breathe. The tank would have been filthy cloudy and stinking when you returned yes?

Most people are surprised when you show them how little food a few fish actally need. A boy would naturally give the fish plenty of food cos it is in his nature i guess.

I wouldn't recommend the food tablest as this can pollute the water too, with all that food sat in the tank. A friend of ours did this and returned to find all his fish dead after a week.

It is much better to do what you did - but to educate the person responsible on how little food they need.

It was indeed cloudy and a little whiffy eric. We only ever feed once or twice a week - took ages to get DD to understand that.

The last fantail has developed fin rot - I am absolutely sure of it. Poor little thing - his lovely flowing tail is all scrappy although he seems fine and is still eating. And the more I read up on it the more mortified I am. It's all down to poor water quality and hygiene or stress apparently . We are scrupulous with cleaning the tank, there's a pump and a filter and we don't overfeed. But we're obviously doing something wrong.

So I'm off to get some treatment stuff from our aquarium shop after work.