The Environmental Gradient

Criticising the Functionality

Some critcism has been made about the potential functionality of this zonal system. I will list the complaints below and respond to each individually. It should be noted that these complaints were from aquarists and captive reef professionals that had not read my recent article in Seascope and had not read any of my books concerning the filtration concept. One has to wonder why professionals that had not read any of the material describing the system have bothered to make public comments, but unfortunately they have been made. These comments are obviously severly limited in content.

With regards to utilizing sponges as a natural filtration component, the following Public Comment was made by a hobbyist:

I have been told or read somewhere that sponges are nitrate factories.

Cryptic sponges are not primary producers. They are heterotrophic and can only acquire food from the water column. They do not have the ability to perform nitrogen fixation. Cryptic sponges cannot release more nitrogen then they acquire from the water column. They can incorporate this nitrogen into their growing sponge matrix. By harvesting the sponge an aquarist removes nitrogen from the system. Sponges release ammonia just like all animal organisms. The nitrogen within the ammonia was acquired from the water column. So no net increase occurs. The true nitrate factories within captive reefs are cyanobacteria that perform nitrogen fixation and the reef aquarist who adds food into the reef. Those sources of nitrogen result in net increases within the captive system. The process of converting ammonia into nitrate is performed by bacteria. In the various test systems I have setup, there has been no elevation of nitrates beyond the limits recommended for maintaining stony corals.

With regards to describing the Cryptic Zones as being efficient filters, the following Public Comment was made by an aquarist:

Cryptic zones in a tank are VERY efficient filters .. that may even work without a DSB, for nitrate removal.

Cryptic zones are NOT specifically setup to remove nitrates. Cryptic organisms or animals are meant to replace the functions of the protein skimmer. The processing of ammonia and nitrate is performed within the zonal system the same basic way it is performed within the Berlin reef system. Live rock provides external surface area and large amounts of internal surface area for bacteria. Live rock is extremelly porous and offers an immense surface area. There have been plenty of captive reefs established without deep sand beds that have maintained very low levels of nitrates. The problem of ammonia buildup within captive aquariums was actually solved decades ago. Every one knows that surface area must be provided for bacteria. This was originally done by undergravel filters and then by trickle filters. Trickle filters were found to produce high nitrate levels over time and their use was eventually replaced by live rock. Great success has occurred with live rock. EG systems utilize live rock methods to establish proper surface areas.

With regards to potentially using sponges as integral natural filtration components of a captive reef system, the following Public Comment was made by a professional:

Sponges do indeed mechanically filter small particulate material in real reefs and in our tanks. This particulate material in our reefs is, of course, the major food for all the other suspension-feeding animals in the tanks such as corals, soft corals, and clams. So, by using a sponge as mechanical filter you are directly impacting other animals in your system by depriving them of food.

If one were to take those statments at face value, the removal of the living sponges from natural reefs could be done to enchance the growth of 'corals, soft corals and clams'. Sponges are integral components of natural reefs. They primarily consume dissolved organics, bacteria, phytoplankton and fine particulate matter. Sponges are active suspension feeders, while corals are passive suspension feeders. New research on natural reefs is beginning to show that sponges are the dominant filter feeders of bacteria, dissolved organics and phytoplankton. Sponges actively pump water through themselves and they have a significantly greater capability of consuming dissolved organics, phytoplankton and fine particulate matter then the passive suspension feeders such as corals. Within the zonal filtration system, cryptic sponges are located within the cryptic zone where they primarily have access to fine particulate matter, dissolved organics and pelagic bacteria. Corals with symbiotic algae can get all their respiratory requirements from their symbiotic algae and all their nitrogen requirements from ammonia within the water column. The ammonia that sponges produce can actually supply the corals with a natural nitrogen source. To state that sponges are detrimental to the functioning of a captive system that is attempting to duplicate a natural reef, is admitting that one does not understand how a natural reef functions. Aquarists that setup and understand a zonal system will have a better grasp of how the various organisms within natural reefs intergrate their functions.