Belgian Anthias
Valuable Member
The role of a skimmer?
My father had a saltwater aquarium in the early 1970s, based on Frank De Graaf's book, manual for the tropical marine aquarium, published in 1969. The aquarium was equipped with a counter-current skimmer. Since then, a skimmer was always in use. What has been established is that accumulation of inorganic nutrients such as nitrate and phosphate has been a perennial theme since then. However, that does not make sense, as the nitrogen is naturally constantly exported through denitrification and in fact a deficiency should occur if natural marine food is used. It is possible that food provided contains far too many of these substances, so that not everything can be used up and left behind due to new growth. Such nutrients then have a very low C/N ratio and usually contain an unnaturally very high protein content.
One can NOT keep fish in a small closed environment without exporting what of the added food was not used by the fish. A skimmer only removes +- 35% at best. of biological waste, whether dissolved or not. A mechanical filter only removes undissolved organic waste. Nothing is removed from what is not in the water column. If all goes well, there is sufficient remineralization capacity and growth, the total bio-load will increase constantly, if not regularly harvested. By using a skimmer, some of the inorganic nutrients and trace elements already present cannot be used up through growth.
Fish are fed and +- 85% of the nitrogen content of the food ends up in the closed environment. Mostly as inorganic nitrogen compounds which are not removed by a skimmer. To remove this nitrogen, of which +/- 15% will escape through natural denitrification, most of the TOC and DOC produced by the fish must be able to be remineralized and reused through growth. This is NOT possible when using a skimmer. Therefore, a skimmer creates an imbalance and accumulation of inorganic nutrients.
Disruption of the nutrient balance by the skimmer makes it impossible for everything to be used up by growth and harvested as needed. Certain nutrients and trace elements can slowly build up in this way to a toxic level.
Removing the skimmer does not restore the existing nutrient imbalance it has created during the period it was in use. This can be corrected by active algae management, AAM
Starting a new system without skimmer?
A coral holobiont will produce CO2 and other inorganic nutrients used by the symbiodinium, a result of remineralization of the DOC available there. Corals are able to supply their holobiont with organic matter and regulate the supply of DOC by excreting mucus. In this way the production of sugars by the symbiodinium is also regulated, a supply of sugars that the coral eagerly uses. A high level of dissolved organic substances in the surrounding water makes it impossible for the coral to regulate the supply as required. Therefore, dissolved organic matter (DOC) levels should be kept as low as possible where corals grow. In the ocean, the level of nutrients present in the surrounding water may be very low, but the supply is inexhaustible.
In an aquarium there is a constant production of DOC.
In the absence of a skimmer, more DOC is produced and more DOC must be remineralized, and more new growth must be harvested to keep the bio-load in check. But the nutritional balance can be restored, nutrient accumulation can be prevented.
Is it feasible to remove the skimmer? Could it solve the decades-long problem of nutrient accumulation?
My father had a saltwater aquarium in the early 1970s, based on Frank De Graaf's book, manual for the tropical marine aquarium, published in 1969. The aquarium was equipped with a counter-current skimmer. Since then, a skimmer was always in use. What has been established is that accumulation of inorganic nutrients such as nitrate and phosphate has been a perennial theme since then. However, that does not make sense, as the nitrogen is naturally constantly exported through denitrification and in fact a deficiency should occur if natural marine food is used. It is possible that food provided contains far too many of these substances, so that not everything can be used up and left behind due to new growth. Such nutrients then have a very low C/N ratio and usually contain an unnaturally very high protein content.
One can NOT keep fish in a small closed environment without exporting what of the added food was not used by the fish. A skimmer only removes +- 35% at best. of biological waste, whether dissolved or not. A mechanical filter only removes undissolved organic waste. Nothing is removed from what is not in the water column. If all goes well, there is sufficient remineralization capacity and growth, the total bio-load will increase constantly, if not regularly harvested. By using a skimmer, some of the inorganic nutrients and trace elements already present cannot be used up through growth.
Fish are fed and +- 85% of the nitrogen content of the food ends up in the closed environment. Mostly as inorganic nitrogen compounds which are not removed by a skimmer. To remove this nitrogen, of which +/- 15% will escape through natural denitrification, most of the TOC and DOC produced by the fish must be able to be remineralized and reused through growth. This is NOT possible when using a skimmer. Therefore, a skimmer creates an imbalance and accumulation of inorganic nutrients.
Disruption of the nutrient balance by the skimmer makes it impossible for everything to be used up by growth and harvested as needed. Certain nutrients and trace elements can slowly build up in this way to a toxic level.
Removing the skimmer does not restore the existing nutrient imbalance it has created during the period it was in use. This can be corrected by active algae management, AAM
Starting a new system without skimmer?
A coral holobiont will produce CO2 and other inorganic nutrients used by the symbiodinium, a result of remineralization of the DOC available there. Corals are able to supply their holobiont with organic matter and regulate the supply of DOC by excreting mucus. In this way the production of sugars by the symbiodinium is also regulated, a supply of sugars that the coral eagerly uses. A high level of dissolved organic substances in the surrounding water makes it impossible for the coral to regulate the supply as required. Therefore, dissolved organic matter (DOC) levels should be kept as low as possible where corals grow. In the ocean, the level of nutrients present in the surrounding water may be very low, but the supply is inexhaustible.
In an aquarium there is a constant production of DOC.
In the absence of a skimmer, more DOC is produced and more DOC must be remineralized, and more new growth must be harvested to keep the bio-load in check. But the nutritional balance can be restored, nutrient accumulation can be prevented.
Is it feasible to remove the skimmer? Could it solve the decades-long problem of nutrient accumulation?
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ratios remain optimal with little mitigation. While I agree that a skimmer may slow the growth of the nutrient reducing organisms, I can't see how some method of control doesn't need to be in place while the populations balance. I've read your posts for a long time and agree with so much of your thoughts. I can't agree that removing only inorganic nutrients with an algae reactor is any better that limiting DOC with a skimmer. Inorganic nutrients are also needed to create the organic compounds that the organisms that balance the C:N
