Dead Fish

[inspiration26]

Hello,

I've noticed that when I go into my LFS, the fish there die and float at the top of the tank. In some stores, I've seen them at the bottom of the tank. I had a platy die once, but it was at the bottom of the tank.

I was wondering if there is some reason for a dead fish to float or sink? Does it give some insight into the cause of death or water conditions or is it totally random?

 

[shelaghfishface]

lol.. morbid!

i guess most float for a while then drop down .. cant say ive ever payed that much attention

 

[Mowbz]

Indeed, very morbid, but the OP makes a good point. Do some float or sink dependant on the condition that killed them? Could be worth looking into.

I've always found mine on the bottom, but ive been at work while they've snuffed it and have often had a few bites taken by passing tankmates by the time i find them.

I suppose it could have something to do with their swin bladder. When alive they have the ability to alter their bouyancy. Not so much when they're dead...

 

[moochy13]

i usually find that armoured fish, like cories and plecs sink instantly. i have never a seen a dead cory floating. i think for a certain period other types of small fish will float, and eventually sink. thats what seems to happen in my experience. if left long enough everything seems to sink. im interested in knowing what happens when big fish die ? if a 6" plus fish dies, do they float ? i have a 6-7 inch syno, and my initial reaction is its big so it would sink, maybe because of the inability to regulate its swim bladder ? but then when i go freshwater fishing, and see similar sized fish floating on the surface, confusing.

 

[raptorrex]

generally speaking. Tropical fish sink, Temperate fish float. though if bacteria build up is big (inside the fish), even Tropical fish float.

 

[Tizer]

Fish that have eaten cake float, but if they have eaten veg, they sink. true story.

 

[inspiration26]

Fish that have eaten cake float, but if they have eaten veg, they sink. true story.

Funny but even thinking of a dead fish makes me queasy and puts me off my lunch

anyhow, was just pondering on whether it has any significance... if this later becomes the basis of some research, you know who to give the credit to

 

[Tizer]

dont worry, i dont think it will

 

[inspiration26]

Actually, disgusting as the topic may seem, it says on other places on the internet that dead fish will sink when they die, and float if they have been left in the water long enough.

So that means, that a floating dead fish in an LFS has probably some bacterial infection, swim bladder, or has not been removed on time



and the topic is best concluded here I suppose. Not the best of things to think over.

 

[soybean]

Presumably a build up of gas inside them causes them to float.

 

[moochy13]

Actually, disgusting as the topic may seem, it says on other places on the internet that dead fish will sink when they die, and float if they have been left in the water long enough.

So that means, that a floating dead fish in an LFS has probably some bacterial infection, swim bladder, or has not been removed on time



and the topic is best concluded here I suppose. Not the best of things to think over.

i lost an emporer tetra 2 days ago. when i went to bed it was alive, when i got up it was floating.

 

[twodoctors]

Presumably a build up of gas inside them causes them to float.

The most plausible explanation so far. It's all to do with density. If the fish is same or more dense than water it will sink and vice versa. So I guess if it's rotten enough inside then it will float. Or if the swim bladder was in the float position it will float.

 

[Mowbz]

Presumably a build up of gas inside them causes them to float.

The most plausible explanation so far. It's all to do with density. If the fish is same or more dense than water it will sink and vice versa. So I guess if it's rotten enough inside then it will float. Or if the swim bladder was in the float position it will float.

Bit of biology (for me if not the sake of others!)

Does a fish's swim bladder have a set pressure that they reduce to "sink" and "inflate" to rise? Or do they simply inflate/deflate as needed.

My thinking is that if it constantly has air in it, and perhaps a muscle contracts to reduce it to sink, if they die, they'll lose this ability and so it will "re-expand", and they;ll float.

I could also be way off base here....

 

[raptorrex]

Presumably a build up of gas inside them causes them to float.

The most plausible explanation so far. It's all to do with density. If the fish is same or more dense than water it will sink and vice versa. So I guess if it's rotten enough inside then it will float. Or if the swim bladder was in the float position it will float.

density has it. cold/er water is more dense than hot/er water. so tropical's sink, temperate float.
bacteria cause gas, so may make fish float. as i stated.

@Mobiz. the swim bladder will fill according to the water density. as far as i am aware, it should give a fish, neutral buoyancy, as standard. lol. the. fish then adjusts to either sink or rise.

 

[HayzH]

i usually find that armoured fish, like cories and plecs sink instantly. i have never a seen a dead cory floating. i think for a certain period other types of small fish will float, and eventually sink. thats what seems to happen in my experience. if left long enough everything seems to sink. im interested in knowing what happens when big fish die ? if a 6" plus fish dies, do they float ? i have a 6-7 inch syno, and my initial reaction is its big so it would sink, maybe because of the inability to regulate its swim bladder ? but then when i go freshwater fishing, and see similar sized fish floating on the surface, confusing.

i have recently lost 6 Panda cories...and all but 1 floated when dead.