Understanding The Nitrogen Cycle
pH Levels (percentage hydrogen)
Most pond fish require a level between pH6.5-7.5. Levels over pH8.5 will cause stress to your fish and restrict plant growth.
Any signs of high levels ammonia should be treated as an emergency situation for fish. High levels of ammonia in pond water are often caused by overstocking of fish or too much uneaten food, fish waste, decaying plant matter etc.
Nitrites & Nitrates
If ammonia in the pond is left untreated, nitrites and nitrates will form. The former are highly toxic and very dangerous to fish. Whilst the latter are non-toxic, high levels will encourage the growth of unwanted algae.