However, this way of doing things really does block off microbial and chemical mediators from performing their processes to their full capability.

I think everyone will agree with me that on Google blogs and post, we still see hobbyists setting up their aquariums with gravel being placed right on top of the glass bottom. This practice is a little obsolete by today’s standards but is still being carried out as if nothing is wrong with this practice. Maybe not knowing or thinking all will be well in the long run.

However, this way of doing things really does block off microbial and chemical mediators from performing their processes to their full capability. This is not a questionable scenario but a scientifically proven fact that this will become eminent in collapsing a biofiltration system. Conversely, before that happens there will become other problems with water quality and fish health that the hobbyist can’t explain before invasive action is take on the hobbyist part to correct the situation. I will explain what happens.

First, the filtration system that you are using now will unquestionably begin to clog and when that happens, oxygen concentrations become depleted where there is no water flow through the substrate and/or filter medium. Nitrogen is then reduced back into ammonium (Assimilatory Denitrification) in a two-step process by obligate anaerobic heterotrophic bacteria, which becomes problematic to the aquarium/pond ecological unit.

These extremophiles under anaerobic conditions that have developed from a clogged filter will not convert ammonium back into a gas element that is released into the atmosphere. I do not know where hobbyist got the notion, that anaerobic conditions will convert nitrogen into a gas element, but I hope we can clear up this matter right now and here, it does not! It just makes more ammonia/ammonium that your system now has to deal with.

This is extremely important because ammonium can be recycled in the filter back into nitrates and either or both nitrate and ammonium can diffuse throughout the filters medium, creating an extremely nutrient-rich filter environment and leach into bulk water. The additional ammonium and/or nitrates that leach into the bionetwork becomes a new foodsource for cyanobacteria and algae alike.

Therefore, it should now be extremely clear just what classes of bacteria exist, where and why and what they can accomplish. However, in most cases our aquariums/ponds contain more bioload than what existing microbes can adequately process into an overall balanced environment within the biotope itself.

It can technically be said that no matter what type or size of filtration that most hobbyists use, the microbial population in the filter will be in equilibrium and/or balance with its supply of foodstuffs.



The blackening of the media is from hydrosulfuric acid caused by obligatory anaerobic bacteria. This will occur whenever free-oxygen is lacking between the liner, rocks, and gravel. ☠



However, this is somewhat misleading because in a close recirculating biotope such as our aquariums and ponds, the overall efficiency of the filter is in relationship to the systems incoming foodstuffs that really counts, not that the microbes themselves in the filter are living together in a balanced state.

Because once nutrient load exceeds the balanced state of the filtration system, (And that degree of balance depends upon what class and the number of microbes exist in the filter itself.) further nutrient results in both the filter and the bulk water.

 Of course, this relates to the bacterium that inhabits the filtration system.

Second, under the same conditions mentioned above, two colorless flammable poisonous gasses, methane (CH4), and hydrogen sulfide gas (H2S) are then created. These two gas elements have been proven to degrade water quality significantly. In addition, forming a weak acid called hydrosulfuric acid and blackening of the substrate can occur due to the lack of free-oxygen in the substrate. Furthermore, methane with ammonia will produce hydrogen cyanide (HCN). Hydrogen cyanide, also called hydrocyanic acid and prussic acid is extremely poisonous to humans and aquatic animals alike. Numerous plant and aquatic animal diseases can be related to such gasses along with premature death, with the hobbyists not knowing or understanding why!

Dr. Kevin Novak Ph.D.

  

 The photo shows the blackening of the stones is from hydrosulfuric acid caused by obligatory anaerobic bacteria. This will occur whenever free-oxygen is lacking between a pond liners or aquariums bottom, with rocks and gravel placed directly on top without a plenum.