Invisible Fish

[sharkman]

I was assigned a biology project where I need to prove wether or not there are invisible fish in my teachers fish tank. The tank has a light, a pump and an air rock that are on 24 hours a day. The tests can in no way harm or stress the fish. I only have a 10ml sample of water on which to perform tests. I know I could test for ammonia from the urine or the carbon dioxide from respiration but I'm looking for something more creative. Anyone got any ideas?

[mith]

How about food, would your teacher feed fish that didn't exist?

[sharkman]

The project is to design an experiment that would prove if there were invisible fish. It's indeded to teach us proper experiment desdign and use of the scientific method.

I did some research and found out that 99.9% of freshwater fish are hypertonic to their environment, meaning they need to pump in sodium to maintain homeostasis. As a result potassium is pumped into the water. Does any one know a way to test for potassium in a small sample of water?

[mith]

I think they pump water out, potassium shouldn't be involved.

[MrMistery]

Freshwater fish are hypertonic to their environment, so they lose ions through diffusion. This is, from what i know, compensated, by drinking water once in a while and not by a cellular mechanism. They don't actually need the extra water, because it enters the guills via osmosis.

-Edited due to temporary stupidity

[MrMistery]

Oh yeah... occam's raisor. Simplest solution tends to be the right one. Mithril is right. Just measure food levels. No need to measure urea or ammonia or other complicated stuff like that. If you really want to measure potasium level use an iron salt to determine it.

[Poison]

Measuring CO2 or O2 levels seemed easier to me but may not sound creative.

[nitrobackflip]

fecal coliform is the best test because it only exists in the digestive tracts of animals - check for colonies, if none are present there is no fish, simple as that

[kotoreru]

I agree with Poison on this one. 02 levels before, 02 levels after - simple.

Failing that, really mock your teacher - just run a net through the tank and see if you catch anything.

(sorry)

[MrMistery]

checking for coliform germs might not be a good idea, since you may discover that your drinking water is contaminated. What you don't know can't hurt you

[daniel.kurz]

If you can't see them they don't exist. Simple taxonomy there is no such fish.

[dr. dugmore]

If you can't see them they don't exist. Simple taxonomy there is no such fish.

does that mean that atoms dont exist? open your mind!!!!


your teacher has came up with a great assignment, let me know how the other people do it, as well as you, not all teachers are as fun as yours!