Salt Water Aquarium Tips and Tutorials

Why do dead fish in salt water sink but fresh water fish float?

I have had both fresh and salt water fish tanks. Every time one dies in the salt water tank it sinks to the bottom (i have a water pump in both tanks) and when my fish die in the fresh water it floats. I always thought it would be the opposite but no! Why does this happen???

The water has nothing to do with it. It is whether the fish had it’s air bladder full when it died or not.
Dead fish in the ocean will float just as readily as ones in fresh water. I’ve seen fish in both types of water float and sink. It also depends on how long the fish has been in the water.
Your observations in your fish tanks is less than scientific I’m afraid, and just a coincidence that you’re seeing what you’re seeing.

I might be getting a 30 gallon fish tank. Is it to small to start a salt water tank?

January 5th, 2009 at 9:24 pm


3 Responses to “Why do dead fish in salt water sink but fresh water fish float?”

  1. dela. soulchild Says:

    Salt water is denser then fresh water..So when a fish is no longer carrying his own weight..the thicker salt water weighs down on his poor little body causing him to sink..
    But fresh water has less salt or none at all..allowing the fish to float on top..
    References :

  2. Nicole P Says:

    its the water
    References :

  3. BWANA Says:

    The water has nothing to do with it. It is whether the fish had it’s air bladder full when it died or not.
    Dead fish in the ocean will float just as readily as ones in fresh water. I’ve seen fish in both types of water float and sink. It also depends on how long the fish has been in the water.
    Your observations in your fish tanks is less than scientific I’m afraid, and just a coincidence that you’re seeing what you’re seeing.
    References :
    Professional Wildlife Cinematographer, Photographer, Naturalist, &
    Director Of Photography Special Visual Effects.

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