Answer:
Ammonia, nitrite and nitrate at higher levels are toxic to fishes in the aquarium.
Step-by-step explanation:
Ammonia,nitrates and nitrites are all byproducts gotten from organic wastes which is biodegraded in the aquarium. These byproducts are gotten from fish and plant wastes, uneaten algae , bacteria e.t.c. There are bacterias in the aquarium that help to break down nitrogenous wastes in the aquarium.
Therefore, the waste from fish and plants are breakdown by bacteria into ammonia.
Ammonia at high levels are very toxic to fishes. Then the nitrifying bacteria then help to convert ammonia to nitrite.
Nitrite also at high levels is very toxic to fishes in the aquarium.
Nitrite is also converted to nitrate by nitrifying bacteria.
Nitrate is not very toxic and it is use by algae or plants for growth in the aquarium.