Saltwater aquaponics?

[grantmcd]

Hi all,
I was wondering what the possibility would be of running a salt water system? So I want to raise salt water fish like sole or cob and I want to know if it is possible and what plants should I use to filter the system?

Any help would be appreciated.

[jackalope]

I've heard of that, and I think there are a few veggie plants that will tolerate the salt water .... I'd Google, Ixquick, or check You Tube to see if I could find any takers

[badflash]

No too many crops that will be worth growing in salt water. There are some chinese plants, but not many. I also have not heard of anyone trying those fish in aquaponics.

[urbanfarmer]

Well, as far as the fish, you could use Tilapia!

http://dx.doi.org/10.1016/0044-8486(92)90253-H

Seaweed is an expensive item, but typically needs to be dried and packaged before it is sold, which may be costly. This would be better marketed toward ethnic communities.

[dufflight]

Few people have talked about it. Think growing seaweed for the regular garden or AP system and take out the solids. If the solids were watered down to dilute the salt if would make a good fert for the dirt garden.

[rfeiller]

twenty-five years ago there was a saltwater set-up in the carribean where seaweed and conchs were grown for commercial purposes. it was at that time quite successful.

as far as tilapia in saltwater, if in hawaii you can find them in tidepools of brackish water. there is a lot more money in abalone, conchs, etc. then in tilapia. seaweed brings in a lot more then lettuce.

[urbanfarmer]

Few people have talked about it. Think growing seaweed for the regular garden or AP system and take out the solids. If the solids were watered down to dilute the salt if would make a good fert for the dirt garden.

ld
The salts would eventually build up to toxic levels and kill off your plants. The salt content would be so high the plants would not even be able to take in water! Remember, seawater is 3.5% salt. If you drink a lot of it you die. For instance, if you drank 6.9 Liters of seawater or your salty aquaponic water, you would end up dead.

http://wiki.answers.com/Q/How_much_s..._kill_a_person (it says 40 teaspoons, I did the conversion for dramatic effect)

Interesting fact: Salt kills weeds, and everything else in the area. In fact, the ancient Romans routinely salted the lands of their conquered enemies. Specifically, they so heavily salted the ground around Carthage that the area is still desert.

http://wiki.answers.com/Q/How_much_s..._to_kill_weeds

Suffice it to say, you don't want to do that. IF you still had your heart set on using the waste product on your garden, you could distill your aquaponic water, which would leave behind the solids (salt and some of the micro-nutrients), and give you some of the other nutrients assuming they didn't volatilize into the atmosphere!

Why do you want to do saltwater aquaponics, anyway?

[rfeiller]

hydroponics is not a closed system, so why is aquaponics? i understand there needs to be a certain level of nutrients in the water to feed the plants, but no matter what, unwanted levels always build up and need to be diluted.

[urbanfarmer]

Ah, it seems my question has uncovered a false assumption you have made by comparison of a similar method of growing.

In hydroponics, you have to change the water because of several reasons, but 1 being coincidentally the same as what I listed above earlier. The SALTS build up that make up the INORGANIC nutrient solution filled with dissolved solids you use to feed the plants. As these salts reach fatal levels, the plants are unable to take up water or nutrients and DIE. So, the only solution is to change the water.

In aquaponics, the nutrients are mainly derived from the processed waste of the fish by microorganisms. The nutrients, although water soluble, are not SALTS, but rather ions that get eaten up by the plants. When nutrients are provided in an ORGANIC form they are readily broken down in organic systems and therefore do not cause fatal buildups if balanced. It's all more complicated than this, but remember, it's a miniature ecosystem you are building! The cycle is self-contained; therefore, you do not have to waste water like that (and in fact is one of the main reasons behind why aquaponics was researched at the University of The Virgin Islands and why it has been so successful in Australia).

With that said, you should watch your levels. If your levels are out of whack such as nitrate, you will want to change out some water. This water can be used to fertilize soil plants or in pure hydroponic systems where relatively high levels of nitrate for fish are inconsequential to the plants. My first aquaponic setup was a 10 gallon tank. I must have spiked the nitrate up to 800ppm at one point. I lost 1 fish of 35; afterward, I used most of the water in a hydroponic DWC bubbler system. The plants did great, and the remaining fish thanked me for it! LOL

[badflash]

You always need to watch your system and compensate. Systems are never perfectly balanced, but the need to do water changes are dramatically reduced in aquaponics. Normally the levels get too low for the plants, not too high for the fish.