Do Fish Always Float to The Top When They Die
By Eddie Waithaka @aquariawise
It hurts to lose your pet fish, but it hurts more when you are sure he (she) is dead, but you can’t find the body.
Well, most fish will eventually float when dead, but they will first sink as their bodies are heavier than water. The remains will only start rising once the body has decomposed enough and become buoyant.
Moreover, a dead fish may sink and get lost in decorations, rocks, or plants in your tank, which may be the reason why you can’t find a body, but some also jump out of the tank to their death, meaning the remains are somewhere outside the tank.
The odor from the decomposing dead fish will certainly help locate your fish if it jumped out of the tank, but you may need to do a little recon work to find a body stuck between or under plants and decorations.
At times, your fish may fail to float entirely, and you may miss it completely, more so if you have a large, heavily planted aquarium.
Now, there are a few exceptions where a fish may float immediately after demise. The exception you are most likely to see is when the ailment or injury that killed your fish also resulted in your fish bulging and compromising its buoyancy control.
For instance, any condition culminating in swim bladder disease and eventual death would result in your dead fish floating instantly.
How Long Does it Take for A Dead Fish to Float in A Tank
Part of your dead fish will need to decompose for it to float to the surface. Depending on your finny’s size, it will take between eight and 14 days in a cold water tank and only a couple of days in a heated aquarium.
Your fish will remain at the bottom of the tank as its body is still heavier than your aquarium water.
Most fish are slightly denser than water, so sink immediately after death. However, like a drowned human, they become more bouyant overtime as bacterial decomposition produces gases in the body enough to make the fish float: Science Focus.
A fish that had gas trapped in its body before death will certainly float a lot quicker, while a fish lost or stuck between, below, and inside decorations will not float.
Since bacteria is responsible for decomposition, I’m guessing if it also caused your finny’s death, the body will have gases, decompose faster and float more readily.
Why Didn’t Your Fish Float When it Died
There are occasions when a fish won’t float once it’s dead. By far, the most probable reason is it has not decomposed yet and will most likely come up to the surface once that happens.
However, if your fish got trapped in a crevice inside the tank and died or died first, then sunk into a thicket or decoration, it might not float even if it decomposes.
The other scenario would be your fish jumped out of the tank and died from the fall, meaning the body is somewhere in your house but not inside the tank.
Given the scenarios above, I like to do a fish count at least once every week, even when I don’t have an injured, ill, or weakly fish in the tank.
It helps quite a lot, more so with skittish fish like kuhli loaches and bristlenose plecos or sick and breeding fish, which can remain in hiding for several hours.
If you have critters (shrimp, crabs) or snails, a headcount is equally crucial since they hide a lot, have tiny bodies, and are prey animals that often get killed or eaten by fish.
What Does it Mean When A Fish Sinks to The Bottom
Fish will sink to the bottom when they are dead, but if they are visibly alive, they are down there because of other reasons.
Loaches, plecos, catfish, and some cichlids love to swim and live at the bottom of the fish tank. They will hide in caves, swim around rocks, and sift the substrate to pick up bits of food.
Basically, it’s normals for bottom-dwelling fish to remain at the bottom of the fish tank.
Even so, if your fish usually hang around the mid or top level of the tank and suddenly start swimming at the bottom, it might be bored, stressed, or sick.
A common disease that would cause this behavior is swim bladder disease. An affected fish will have buoyancy issues that may cause it to swim to the bottom of the tank, float at the surface, float upside down or on its side and struggle to maintain normal body position.
A fish with another whirling disease, a rare ailment but similar effects, may cause your fish to swim in a downward corkscrew motion, though they rarely stay at the bottom.
I mentioned your fish might also remain at the bottom of the tank if it’s bored or stressed with its environment, but it does not remain floating in one place.
A stressed fish will surf the glass in an up and down motion, almost like it sizing something outside the tank.
Given all these scenarios, if your fish is floating motionless at the bottom of your fish tank, especially if it’s an active species, check the gills to make sure it’s breathing.
If there is no gill movement and body movement generally associated with a live breathing animal, and the fins and tail are lying still, then your fish is very likely dead.
But if the gills and body are moving in a breathing motion, your fish is alive. Maybe the fish is just resting or sleeping, even though stress and sickness may also manifest similarly.
To make sure your finny is not sick, observe him for a couple of days and be ready to take appropriate measures if you are convinced your fish is ailing.
How Do You Know Your Fish is Going to Die
Fish are graceful, low-maintenance pets, but their subtle demeanor also means finnies can hide illnesses pretty well.
Mostly, they conceal ailments to avoid looking weak because they will get picked on by other members. Fish exist in a hierarchical society where illness is a sign of weakness.
So, as a fish owner, you need to keep an eye on all your finnies and master their behavior, so you know when one is sick. If you are not careful, by the time you realize your fish is ill, it’s might be only a short way away from dying.
A sick fish close to dying will look weak and may have difficulties swimming. Your finny may also lose appetite and hide behind plants and decorations more than usual.
If the fish develops conditions like swim bladder, dropsy, or bloat, they will have a swollen abdomen and most likely lose balance or buoyancy control.
Floating upside down, sitting at the top or bottom of the tank, and erratic spiral swimming are also signs your fish is ill and possibly dying.
If whatever is causing you finny’s ailment has also affected your fish’s internal organs, your fish might gasp for air and breath heavily (abdomen moving up and down rapidly).
Organs that are most time affected, more so by toxic elements in the water and may cause your fish’s untimely death, include gills, liver, kidney, and eyes.
Scales, skin, and slime coat damage may also indicate a fish is hurt or sick, and it perhaps might die if not treated.
Possibily, the last (and arguably the most obvious) sign your fish is dying or dead is a lifeless floating finny with almost zero body movement.
The gills and fins will remain unmoved even when the other fishes come around, and the abdomen remains still or move sluggishly.
When your fish finally dies, the body will most likely sink, but it might float the cause of death is something like bacteria which creates air and fluids to accumulate in the body cavities making the body buoyant.
That’s all for this article.
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Happy fish keeping🐠🐟.