An ammonia spike can develop for a number of reasons:
a new tank will not have developed the bacterial capacity to
convert ammonia to nitrites and nitrates
medications can kill helpful bacteria and prevent conversion
of ammonia
overfeeding can increase ammonia
adding more fish causes ammonia levels to increase
temporarily as bacteria adjust to the new ammonia volumes
The ammonia level and the nitrite level should be zero in a saltwater tank. Nitrate levels should be
zero for a reef tank and under 30 ppm for a fish only tank. Here are some things you can do to help correct
problems in ammonia levels right away:
Remove waste with a protein
skimmer. If you don't have one, it's time to invest.
Do a 20% water change with premixed saltwater and continue
to do this every day until the ammonia level drops.
Test the water daily for ammonia levels. If they
remain high, you'll need to change more water. You can also use Seachem
Prime.
Keep good aeration in the tank to help develop bacteria.
Avoid using medications, as these kill bacteria.
Don't feed your fish at all if your ammonia readings are
high, as this will cut down on the ammonia that the fish produce.
Don't clean the sand or remove live rock. You want to promote bacteria
and these are excellent location for this.
