Are reef tanks carbon limited?

[Miami Reef]

A few questions:

1. Do natural shallow reefs use bacteria or phytoplankton as food? I think I read that bacteria is predominantly used in shallow reefs, but I want to make sure I didn’t misinterpreted that.

2. Are reef tanks carbon limited?

 

[ReefGeezer]

A few questions:

1. Do natural shallow reefs use bacteria or phytoplankton as food? I think I read that bacteria is predominantly used in shallow reefs, but I want to make sure I didn’t misinterpreted that.

2. Are reef tanks carbon limited?

I don't know about real reefs, but organisms in mature reef tanks can and do use bacteria and Plankton (Phyto and Proto) for food. It also seems that Heterotrophic Bacteria (as well as other heterotrophic organisms) can grow very quickly in reef tanks to consume organic carbon and make the systems perpetually carbon limited.

 

[Randy Holmes-Farley Verified Community Expert]

A few questions:

1. Do natural shallow reefs use bacteria or phytoplankton as food? I think I read that bacteria is predominantly used in shallow reefs, but I want to make sure I didn’t misinterpreted that.

2. Are reef tanks carbon limited?

On number 2, that’s too vague to answer. Some organisms are organic carbon limited, such as many bacteria.
Most photosynthetic organisms are not organic carbon limited, but some algae may be inorganic carbon limited. Fish are likely carbon limited, as are people (if I eat a lot of sugar I’ll grow fatter).

Many hard corals are alkalinity limited, which one might think of as inorganic carbon limited, although not in the standard sense since CO2 doesn’t help.

many other organisms can be limited by trace elements, or light, or space.

 

[Randy Holmes-Farley Verified Community Expert]

On number 1, there are lots of studies on what is found in the digestive tracts of organisms in the ocean and it varies a lot depending on what organism you are looking at.

 

[taricha]

1. even within corals, some feed more on copepods, which are driven by phytoplankton, some on phytoplankton directly. Others consume most of their particulate carbon through eating bacteria. Not sure it makes sense to maximize either to an extreme.
And the hobby has selected by survivorship bias, corals that can survive well on light alone for their nutritional needs, because those that need particulate foods just die too easily.

2. To answer it from another angle than Randy, reef tank water is organic carbon limited in almost all cases.
By which I mean you can easily find NO3 or PO4 laying around in the water, but if you do a 3 or 5 day BOD test on reef tank water - to measure the O2 consumption occurring in a water sample (from metabolism of organic carbon), it's pretty small - like 1mg/L O2 or less. If you add more NO3 or PO4 to the water, it'll often be stable. I had test tanks circulating in the dark that kept ~50ppm NO3 unchanged for months. But if you add some acetate or ethanol or glucose to anybody's reef tank water, stuff will grow and the organic carbon will get processed.

 

[sixty_reefer]

2. Are reef tanks carbon limited?

Some may be, some may not be carbon limited.

If we were just talking about bacteria, we would have to look at all 3 nutrients as our aquariums could become limited by any of them at any point in time.

 

[Hans-Werner]

1. Do natural shallow reefs use bacteria or phytoplankton as food? I think I read that bacteria is predominantly used in shallow reefs, but I want to make sure I didn’t misinterpreted that.

Please see here. I think Sorokin has done a lot of experiments with radioactive tracers.

I still rate Sorokin's book on Coral Reef Ecology very high. It is one of the first and best to explain the whole food, nutrient and biochemistry processes occuring in coral reefs in a very coherent and enlightening way. His book delivers really a holistic approach.