Primary food sources.

[Belgian Anthias]

Feeding an aquarium? Must we continue to feed the end users directly, wasting + 60% of the food, or can we feed the primary food sources needed for producing natural food for the end users. Will it make a big difference in managing the nutrient content of the system?

Using a refuge for managing growth rates and nutrient reserves in the system? It can be done by giving the refuge what it needs to maintain sufficient growth, to maintain enough growth making it possible to manage the nutrient reserve in the system. It is easily done using modified media used for fythoplankton cultures, F medium , Von Storsch medium ( VSE), or any other suitable food medium.

I think it is possible to provide the system with enough natural food for feeding the end users just by adding what is needed, what is finally stored in growth.

 

[ichthyogeek]

So like...directly adding phytoplankton and other primary producers (including detritivores like bacteria) to the tank instead of just fish food?

I mean, you could, but it'd be hard and probably look super messy.

 

[Belgian Anthias]

Avoiding nutrient build up by just adding the building materials needed to support growth of primary and secondary producers (phyto- and zooplankton), taking in account the available nutrient reserve. This way the nutrient reserve and balance can be managed as desired. Micro and macroplankton will feed the endusers. Waste products are recycled and reused as always.
As nutrient buildup is easily avoided it eliminates or limits the need for nutrient export .
No need for nitrogen or and phosphate export. If too much it is not added, very simple.
Feeding is limited to a few drops. of medium No mess at all.
Nature will do the rest, providing balanced natural live food.
Just needs introduction of target specimen and a saltmix supporting growth to get started.

Will in this setup the use of a skimmer be usefull or be contra-productif?

 

[ichthyogeek]

So adding in F/2 or a similar situation. I doubt it. As time goes on, more unpalatable algaes will start to take hold, stripping the nutrients intended for the microalgae used.

A skimmer would only function to strip organics and microplankton from the water, which you already stated should be “recycled and reused as always”.

 

[Belgian Anthias]

So adding in F/2 or a similar situation. I doubt it. As time goes on, more unpalatable algaes will start to take hold, stripping the nutrients intended for the microalgae used.

A skimmer would only function to strip organics and microplankton from the water, which you already stated should be “recycled and reused as always”.

Sufficient growt is maintained in a reguge to , it will be inpossible for unpalatable algae to strip all the nutrients; it is the intention to culture the target primary and secondary producers

I think, always species will try to become dominant. As it is just a matter of time, the advantage of feeding a balanced medium, cultivating primary and secondary producers in a refuge, will be the high competition between palatable species of our choice and other organisms due to maintaining a high growh rate by feeding palatable species in a refuge, the feed can be managed easily. No feed is wasted and the feed can be modified for correcting the nutrient balance and the nutrient reserve in the system. Palatable growth can be harvested and reused as feed, as desired . The cultivated palatable growth can be anything, micro- macro- algae, biofloc, or a mix.

 

[Belgian Anthias]

Managing a closed system one is aware that at some point drastic changes and adjustments must be made. In aquaculture systems, this is done by harvesting everything when growth becomes insufficient and a new batch is started. In aquaria we try to maintain growth as long as possible.
In that perspective an aquarium system must have the ability to grow and support the constantly increasing bio-load. Making the carrying capacity easily manageable and controlable may help to delay the inevitable for a very long time.

My biggest concern is the carbon cycle as most carbon is exported as CO2. It can be imported the natural way or by food.
I think the problem will be to import enough carbon the natural way to support the foodchain of a mixed reef aquarium.
F/2 medium does not contain the carbon needed.
Adding carbohydrates provides a carbon source for wich not much energy must be spent. The problem is to know how much may be added to keep the balance.

Very important is the DOC level as corals are very sensitive to high DOC levels, it disturbes the propper functioning of the coral holobiont.( ref: MB Anthias 2019)
Keeping DOC very low is not difficult using a good remineralisation filter, this includes CO2, Ammonia and Phosphate production, ammonia which is imediately transformed into usable safely stored nitrogen in nitrate, the endproduct of compleet remineralization.

Bacteria breaking down organic waste can only make use of DOC ( dissolved organic carbon), To transform organics into DOC a lot of energy is spent before they can use the available carbon to make energy and to grow. That moment they are spending their energy reserve, a critical period. Sometimes more carbon is used to make energy as taken up to grow, all that carbon , not taken up to grow, is transformed to CO2. This also means that a lot of the buildingmaterials present in the organic waste can not be used for growth at that moment and stay available in the water column, including nitrogen and phosphorus.
The origin of the food source therefore is very important, for the foodsource to become a carbon sink or not. Using terrestial food sources must be avoided. Using primary feed media containing organic carbon may help solving this problem.

Using a good remineralisation filter it is assumed everything is completed and a low DOC level is maintained, the produced nutrients left over can be directed to where they can be used up, only what must be added to maintain sufficient growth must be supplemented using primary food media.

I think, removing organic waste before it is turned in to DOC is important once the desired food chain is installed. A lot of DOC is not the result of bacterial acivities. So, removing organic waste as fast as possible seems to me the most productive for limiting the carbon sink.