I might be completely wrong but from what I know the nitrite level is the one that is important and that level will be effected by the condition of the bacteria in your bio system. A bakke shower will help for this because it will allow more surface area for the bacteria.
The nitrate levels is an indication of the health of your bio system globally and this level will promote algae blooms unless you have sufficient plants to extract the nitrates from your water.
Amonia will disperse into the atmosphere through natural gas exchange and will become threatening if you do not have ample exchange opportunities. Large surface areas are natural exchanges but you can increase this with showers, waterfalls, streams and venturies.
DOn't be tempted to chase the processes of removing the three, amoniac, nitrites and nitrates with chemicals. As long as you have the right bio elements in place and enough plants the natural processes will very quickly set the balances right. The easiest way to protect your fish while the bio system catches up is to cut back on feeding the fish.
Just my 2 cents.