|I'm doing my science fair project on 'does the
color of the water effect the fish's life span?'
using food colouring to dye the water do you
think this will kill them?
|Question Date: 2007-02-01|
I think (I hope!) that any food coloring you can
buy in a store is nontoxic for humans. This
probably means it is also nontoxic for fish,
although you never know -- that's why it's good to
do experiments. But I suspect that simply putting
fish in dyed water probably won't hurt them too
much. However, many fish rely on vision to find
their food, so if the water is so heavily dyed
that they can't see very well, then they might
have trouble catching prey and won't grow very
much. They might even starve to death, if you ran
the experiment long enough. To see this effect
you'd probably have to feed fish live food, like
brine shrimp, instead of just using fish flakes.
If you're planning to buy your fish from a pet
store, I would explain your project to someone who
works there -- he or she might have some good
ideas about what kind of fish and food would be
best to use.Good luck with your project!
This is a great idea for a topic.I would not use
food coloring, mainly because you can accomplish a
similar objective without it. Food coloring is
generally harmless, but it may be toxic to
fish...you never know.
What you must
consider is what you mean by "color of the water".
Water (H2O) does not have much color
because it does not reflect light very well. When
the ocean looks blue, it is actually just that it
absorbs almost all of the other colors completely,
and reflects a tiny bit of blue back at your eyes.
This is why deep water looks blue and a cup of
water looks clear.
When you put food
coloring in water, you are adding material which
reflects a certain color of light (a certain
wavelength) very well, but also absorbs other
colors. For the fish, you are mainly changing the
AMOUNT of light which reaches the fish, and then
secondarily changing which colors reach it.
A better option would be to find
translucent plastic in different colors to wrap
the fish tank in or to put over the lights shining
on the different tanks. You can also get
different colored bulbs at pet stores. These
plastics will selectively allow different
wavelengths of light to pass through while
blocking the rest, so that the light you see has
many components completely removed and looks a
single color. This way the fish is getting just
one main color of light. You can use colored
plastic wrap (Available at grocery stores) or get
plastics of different colors at a hobby store or
craft store. Remember, they have to be thin and
If you're using food coloring intended for human
consumption, and don't use more than a couple of
drops, they'll probably be fine. My question for
you is what will this tell you about fish? When
scientists do an experiment, they generally have a
question or guess (hypothesis) that they are
trying to investigate. Why do you think water
color will influence lifespan?
I know you
will be taking good care of your fish. They will
probably all still be alive at the end of your
experiment, which is a good thing. However, if you
are looking at how color influences their
lifespan, you probably won't have an
I suggest studying something about
your fish that will give you guaranteed data right
away. For example, do they find one color food
faster than another color? That will tell you
something about fish vision and hunting. Do they
find food faster if the color of the food is the
same as the color of the water? You would still
be changing water color, but could gather data
every day and also learn about fish vision. If
you provide them with gravel or backgrounds of two
different colors, where do they spend more time?
That will tell you about the habitat preferences
of fish and whether they prefer one color over
another. You could also do that experiment using
lights of two different colors shining on two
different ends of the tank, but you would have to
monitor the temperature.
Can you think of
other questions that you will be able to answer
between now and when you have to prepare your
presentation or paper? Feel free to ask more
questions when you have more ideas.
The short answer to your question is: not unless
the dye is toxic to the fish. Some dyes are
thought to be toxic, especially the ones used in
fabrics. The dyes used in food coloring shouldn't
be toxic to humans, because we eat them. This
doesn't necessarily mean that they are not toxic
to fish. A better question for your science
experiment might be: are food coloring dyes toxic
to fish? If so, which colors, and at what
As long as the water is
the same in every other sense (same oxygen
content, same food content, same pH, same
concentration of salts, same temperature, same
fish tank, etc.), then the color of the water
shouldn't make a difference if the dyes are not
toxic. However, this is kind of an interesting
question, because in the ocean, what changes the
color of ocean water is the stuff in it, and this
stuff can affect food content, oxygen content and
pH, so the natural color of ocean water does have
some effect on the fish that live in it. I'll tell
Pure, crystal clear ocean water
When you add mud and dirt, the
water turns a yellow/tan/brown color. This dirt
can clog fish gills, which cause the gills to not
work as well, which can slowly suffocate the fish.
Usually, the dirt and mud gets washed in from
rivers, and the stuff that gets washed in with it
can cause bacteria to grow. Since bacteria use
oxygen, too much bacteria in the water can cut
down on the amount of oxygen available to the fish
and the fish don't do well. Also, the dirt and mud
shade the water, so plants can't get enough
sunlight, which reduces food and oxygen, since
plants make oxygen.
When you add a lot of
algae, the water turns green. Some fish eat algae,
and some fish eat things that eat algae, so this
can increase their food, and their oxygen. This
will increase the health of the fish. However, too
much algae and the bacteria grow again, especially
when the algae dies. (Bacteria feed off dead
stuff.) The bacteria will eventually take up all
the oxygen in the water, which will cause the fish
to suffocate. This is why you have to clean your
fish tank all the time.
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