January 14, 2013 Aquaponics No Comments

After reading a few articles, I came across some very intriguing information on salt water aquaponics. They discussed how using seaweed in these systems is extremely beneficial for both the environment and humans in several ways. There are a few words with (*) next to them meaning you can find their definition at the bottom of this post!

According to an article from 2005, 7 million tons of edible seaweed had been produced in China for human food, livestock fodder* and for soil fertilization.

An edible seaweed crop can be grown in only 6 weeks.

The role of seaweed in a commercial aquaculture is the same as in nature — the uptake of organic wastes that would otherwise pollute the water; seaweed is nature’s nutrient capture system.

The waste of every ton of fish could produce up to seven tons of plant material such as lettuce in fresh water aquaponics and edible, aquaponic seaweed in salt water aquaponics systems. 10 tons of fish in sea water were producing 40-80 tons of edible seaweed from fish wastes which was growing 4-8 tons of abalone*.

Edible seaweed can be used to grow mollusks* or other valuable food crops, or can be used for either human foods that replace salad vegetables or for domestic livestock fodders and soil fertilizers.

Many types of seaweed produce the most valuable omega-3 oil; it can therefore replace fish oil in diets for fish and humans to better balance with the omega-6 oil that has become out of balance with the needs of human nutrition. Omega-3 oils will play a vital role in future human health.

Aquaponic food production systems are kinder to the environment and are healthier for humans.

Not only is seaweed used for edible purposes, but scientists have developed a method to create biofuel* from seaweed; seaweed is now a contender for supplying the world with “real renewable biomass”.

How is this possible?

Well, a new strain of E. coli bacteria has been genetically engineered which can feed on the sugars found in brown seaweed and transform those sugars into ethanol*. This is an incredible finding as using seaweed overcomes land use and energetic constraints of current biofuel production, meaning that there is no demand for fresh water resources– perfect for those areas where it is difficult to attain fresh water. Another plus is that seaweed does not contain lignin* (which is found in many plants) which means that more of its biomass is available to produce ethanol; each unit of seaweed contains more potential ethanol than corn or switchgrass. Seaweed also contains alginate* which can be converted to ethanol in a similar method to making beer; alginate sugars are fed to bacteria in an environment without oxygen, it then ferments the sugar and produces ethanol. Overall, seaweed is an amazing option to use as a source of ethanol; it provides more fuel than plants with lignin and doesn’t require converting any land away from food production.

Are there any concerns when it comes to salt water aquaponics?

When it comes to salt water aquaponics, the systems are often directly linked to an ocean. Sea cage aquaculture can be intrusive to tourist and fishing recreation areas. However, what if a pipeline from the sea took pristine seawater to a pond aquaponics system? It would not get in the way of anything, and in turn fish, seaweed, crustaceans*, and mollusks can be grown. The water going back into the ocean will only have a slightly altered balance from the organisms using up things such as calcium, phosphorous and micro-nutrients.

Will my fish and plants survive in my own at-home salt water aquaponics system?

First of all, ensure to keep an eye on your levels and make sure everything is balanced- you can always change out some water if you need to and use it to fertilize soil plants. You shouldn’t have to worry too much though; salt water aquaponics works the same way fresh water aquaponics does. Ammonia comes from the gills and waste of the fish which is then converted into nitrates by bacteria and absorbed by the plants. When the nutrients are provided in organic forms they are broken down into organic systems and will not cause fatal buildups if they are balanced.

What type of fish should I use?

A common fish to use in a salt water aquaponics system is Barramundi, also known as Asian sea bass. They can grow quite large, the largest line-caught being 44.6kg, and have an eating quality rating of 8 out of 10. It is recommended that they are kept in setups with at least 500 liters.

What are your thoughts on salt water aquaponic systems? Would you prefer having your own fresh water or salt water system?

A few definitions:

Abalone
A common name for any of a group of small to very large edible sea snails; an edible mollusk of warm seas that has a shallow ear-shaped shell lined with mother-of-pearl and pierced with respiratory holes
Alginate
Anionic polysaccharide distributed widely in the cell walls of brown algae, where it, through binding water, forms a viscous gum. In extracted form it absorbs water quickly; it is capable of absorbing 200-300 times its own weight in water.
Biofuel
A fuel derived directly from living matter.
Crustaceans
Class of mandibulate arthropods including: lobsters; crabs; shrimps; woodlice; barnacles; decapods; water fleas.
Ethanol

Ethyl alcohol: the intoxicating agent in fermented and distilled liquors; used pure or denatured as a solvent or in medicines and colognes and cleaning solutions and rocket fuel; proposed as a renewable clean-burning additive to gasoline
Fodder
Food, especially dried hay or feed, for cattle and other livestock.
Lignin
A complex organic polymer deposited in the cell walls of many plants, making them rigid and woody.
Mollusks
An invertebrate of a large phylum that includes snails, slugs, mussels, and octopuses. They have a soft, unsegmented body and live in aquatic or damp habitats, and most kinds have an external calcareous shell
Written by Aquaponics Team