How do you get rid of the amonnia in your fish tank that is turning your fish black?
There are three major reasons you can have high ammonia in your
tank.
First, you could have a dead fish in there. When a dead fish
rots it makes ammonia. LOTS of ammonia. So, check your tank for
dead fish.
Second is overfeeding. The food the fish don't eat sinks to the
bottom and rots, and rotting anything makes ammonia.
Third is that you put too many fish in the tank too soon after
you got it. There is a process going on in your tank called the
nitrogen cycle. Not to put too fine a point on it, but fish pee has
ammonia in it, like all pee does. There are bacteria in your tank
that convert the ammonia to nitrites, then to nitrates, and finally
to nitrogen which evaporates into the air. If you put in all the
fish you want to have right after you get the tank set up, this
cycle (which takes some time to get started) doesn't have a chance
to get going and you get high ammonia levels.
My advice would be to move the fish to a different
aquarium--right now, a 5-gallon bucket with dechlorinated water in
it and a power filter on it will work as long as you've got small
fish--break down the tank, wash the gravel really well, set the
tank back up, put "cycle aid" in it to get the nitrogen cycle
started quickly, then put half the fish back in the tank in two
days. After a few days put the rest of them back.