I’m often asked about the implications of a site away from the ocean, where pumping fresh seawater from a wharf is simply out of the question compared to a sea-bound site.
The obvious implication is the level of water recycling that is imposed by land-based facilities. In these, water must be 100% recycled, or very close to it. This high level of water reuse opens up a leeway for temperature control. Indeed, regardless of the ocean temperature, lobsters can be kept in stable chilled water without spending the extra money for chilling the incoming water. The chilling energy is solely used for neutralizing heat gains from the pumps, air, and the surfaces (walls, ceilings, ground).
On the other hand, a land-based lobster tank implies a complete water recycling system. Some call it a RAS (recirculating aquaculture system). We call it an REBF (recycling with biofiltration) system. A biofilter is a must in such a facility, while in sea-bound sites, the level of ammonia is controlled via dilution with fresh seawater.
Let’s talk about biofilters. These nitrifying bacteria use ammonia as their food. Since ammonia (NH4) does not contain glucose, as for heterotrophic bacteria, it provides very little energy. Consequently, nitrifying bacteria are very slow growing organisms. Furthermore, in cold water, their growth rate declines even more.
So if you try to establish a new biofilter into a lobster pond waiting until the surfaces of the biofilter are coated with these good bacteria, you can consider waiting about one year. Ammonia fluctuations are sure to happen during that year. Further, even when a biofilter is well established, the reaction of these slow-growing bacteria to ammonia fluxes is slow. This occurs when a large load of lobster is transferred into an empty tank, for instance.
In conclusion, 1) a biofilter must be coated with active nitrifying bacteria before lobster is added to a new system and 2) a stable load of lobster is best for a closed system. For instance, keeping lobsters long-term works well in closed water recycling systems. They are not recommended for purging tanks, however, where the animals are put in and out of the tank, carrying heavy loads of ammonia. In a closed water recycling system, one should be attentive in keeping a stable load ammonia. Lobsters can transit in the pond, but the total biomass load should be kept as stable as possible.
The good news is that at AQUABIOTECH, we’ve known this for a long time. All of our biofilters are pre-coated with live seawater nitrifying bacteria before they are put in service. We have even developed a Biofilter Inoculation Station (BIS) designed for lobster ponds. It automatically feeds the biofilter with increasing loads of ammonia until the bacterial population demonstrates that it is ready to work.
As for the optimal management of the closed lobster pond, we provide guidelines to our clients. The main ones being to add purged lobsters to the pond and avoid emptying the whole pond at the time.