Where does ammonia come from?
Shellfish naturally produce ammonia as a waste product. If ammonia is allowed to build up in the water it becomes toxic and can seriously affect the health of your shellfish.
Animals that are already stressed will produce even more ammonia. Common causes of stress include capture, transport and long periods out of the water. Extreme weather can also have an impact. Very hot sunny conditions or strong winds can dry shellfish out and increase stress levels.
Imported lobsters can be particularly challenging. Lobsters arriving from Canada may have been out of the water for several days before reaching your premises. Once they are placed into a holding tank they can release a significant amount of ammonia into the system.
How does a biological filter remove ammonia?
All Todd Fish Tech shellfish holding systems, including the Lobster Pod stacking system and Crab Pod tanks, include an integrated biological filter.
Inside the moving bed biofilter are thousands of pieces of specialist media that provide a large surface area for beneficial bacteria to grow. These naturally occurring bacteria consume the ammonia in the water and begin the biological filtration process.
The nitrogen cycle
The ammonia is first converted into nitrite.
Although this is an improvement nitrite is still harmful to shellfish if levels become too high.
A second group of beneficial bacteria then converts the nitrite into nitrate. Nitrate is the least harmful form of nitrogen found during the filtration process and is much safer for shellfish.
Why are water changes still important?
In the natural marine environment, algae and seaweed use nitrate as a nutrient. Inside a shellfish holding system there is no natural mechanism to remove it so nitrate will gradually build up over time.
Once nitrate levels become too high a water change is needed.
For lobster holding we recommend changing at least 20% of the water every month. Crab generally produce much more waste than lobsters so more frequent or larger water changes are recommended.
As a general rule larger water changes will help maintain better water quality and healthier shellfish.
