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My wife and I love seaweed. We used to go to this Korean store down the street and buy fresh seaweed to put in soups and salads. Unfortunately, they've stopped selling it. I don't know why, I could guess because of the Fukashima issues with contamination of their waters or maybe it's just not selling well enough. Either way, we found that getting fresh seaweed is expensive. The only online stores that sell it are in Maine or California and at ridiculous prices. So we decided that maybe we can try to do saltwater aquaponics/bioponics.

I know others have done this, but unfortunately, they haven't given out any knowledge to help others (that I can find).

It is my hope that because there is so little information available on how to do this, that we will attempt to do the research and testing to see how this can be accomplished and publish our findings to the world so others can duplicate our efforts without the trials and errors that we already went through.

We are also hoping that others will do this or already are doing this and can give us some advise or pointers so we don't make every mistake in the book. If anyone is knowledgeable on seaweeds and their growth habits, that would also be very helpful if you would give some input.

So this will be our setup...

Everything will be grown in our greenhouse in the 7a climate in the US.

A 55 gallon plastic white drum (white so it doesn't get too warm). We will cut the top 1/3 part off and use that as the "grow bed" and the bottom 2/3 part as the reservoir/nutrient tank. We thought about using  saltwater fish but since I am completely ignorant on how to raise saltwater fish, we thought it best to use aged urine as the main nutrient source.

It will be a deep water continuous flow (not ebb and flow) with a small 12w 200 gph water pump, pumping from the bottom tank to the top and it will flow down through a 3/4" PVC pipe back to the bottom tank again. The top bed will have large rocks for the seaweed to anchor itself to it.

For the choice of seaweed, we think Dulse and Sea Lettuce would be best for consumption.

We do not know yet whether these two different types of seaweed require different environments (salinity, ammonia levels, nitrification, etc.) so we may need to build two systems to sustain each one separately.

I have read that Sea Lettuce can absorb straight ammonia and nitrification is not necessary for it's growth. I want to test that by not having much media for nitrification and using aged urine as the primary nutrient source. The only other input would be Aquarium/Ocean Salt (to maintain the proper salinity that seaweed requires) that I will purchase online. I will be measuring salinity with a cheap hydrometer.

I am currently negotiating with some seaweed sellers in Maine for a piece of Dulse and Sea Lettuce and am awaiting a quote.

Feel free to comment or discuss.


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The type of seaweed you like eating, is it Dulse and Sea Lettuce?

You can probably find a bit of information on it's growth habits and requirements just by googling.

I might caution that you may need more water and a way to keep it cool.  Think ocean waters off California and Maine are cold waters so the greenhouse may be overkill during much of the year in a 7A climate and you will probably need to put efforts into opening up or cooling the greenhouse during summer and perhaps even some spring and fall depending on the particular weather that season.  Winter is probably the only time you will really need the greenhouse.

Of course that is just my guess based on where you say you can get the seaweed.

Good Luck with it.  You might look into asking around on some saltwater fish keeping forums and such to see if anyone into planted saltwater tanks knows much about edible seaweeds you can grow.  Actual aquaponics with salt water has been extremely limited and new options are desirable.  So far the only attempts I've even heard rumor of have to do with algae or mangroves.

Hey TC, as to the types of seaweed we enjoy, we've never tried sea lettuce or dulse raw but I heard great things about their versatility (fry, dry, bake, flake, raw, boiled, cooked, etc.)

As to it being too hot, yeah that is a major concern so we may have to do this indoors (with fluorescent lights) or an in-ground pond for the nutrient tank. We have a 600 gallon pond that isn't being used so that might be the solution for the summer-time. I started looking into saltwater fish forums and sure enough, a few people have grown sea lettuce, so it may be doable. Thanks for the input!

Well, after learning that two little pieces of seaweed will set me back $212.00, due to the overnight shipping and such, I've decided that I'm going to have to make the trip to Maine myself to avoid the insane shipping costs. This will have to wait for another time I guess.

If anyone still has any good advice or lessons learned, please feel free to add to this discussion so that someone else may still benefit. Thanks

Start looking into freshwater plants that might "substitute" for seaweed.

There are so many plants you can grow using aquaponics that are great.  Water chestnuts are a great one, they like the hot weather so I have bins that in summer the water chestnuts grow and in winter the watercress goes nuts.

Have fun, try lots of different things and maybe you will eventually have a vacation that takes you where you can get your seaweed.

I like the concept , but am. In a tropical climate . What's the venue u might suggest in a warm 12 month season? :D

So i have grown many species of algae sea weed and mangrove tho not in a traditional aquaponic setup but with a salt water version using a grass bed for filtration. macro algae and sea weed can be tricky but once you get the conditions of your water perfect they will grow like you wouldn't believe. Its alot different tho you don't want nitrates at all in salt water in the ocean there is always enough bacteria to consume any nitrogen saly water creature are very sensitive to this and you need to make sure your dosing idoine to help your seaweed and macro algae grow faster and healthier there is alot more to salt water than a fresh water aquaponic system. Your also going to need a protein skimmer and i would recommend for a large system a calcium reactor to make maintaining your calcium and magnesium alot easier. Have you kept salt water before? If not you might want to setup a salt water fish tank for a few months until you feel comfortable with the difference in chemistry. If you want to learn more read up on reef tank chemistry to better understand what you will need to maintain to grow macro algaes and sea weeds. Alot of them are just as tricky and keeping a coral so your water conditions are far more important than a fresh water system. I'd love to answer your questions.

We tried to grow seaweed in saltwater AP using two IBC totes, one for the fish and the other for the seaweed. Unfortunately we had many problems. Temp and pH were difficult to control and nutrients seemed to be zapped pretty quickly.

Our experiments done in the ocean provided much better results. The best being in a semi enclosure like a lagoon. The second best practice was open-sea plantings under cages...but that doesn't really help your situation.

I too wish I had a better answer for you.


PS might I suggest trying fresh water algae. Doesn't quite taste the same nor is the texture the same but quite nutritious and can be made into sheets like Japanese nori.



Have you considered growing the Superfood Spirulina?


There are instructables online for growing at home. And more details for extended farming. 

Here's a link to a good 15 step setup.


Spirulina starter cultures are widely available through health food outlets.


And here's a pretty informative blog on the subject.


Spirulina CAN be used to augment the fish feed in our AP systems.

AND it IS pretty good stuff.

Just a thought-- Salicornia and Salsola soda are both edible (quite tasty, too) terrestrial plants that have high salt tolerances. They are sometimes marketed as "alghe" in Italy, and served in restaurants as side dish/veg accompaniments with main courses. I think they might grow in a media-based saltwater AP system. I will be experimenting with Salsola this season (but in my FW system).

Dr. Edoardo Pantanella  PhD,University of Tuscia, Viterbo, Italy was doing some research on saline aquaponics in Tiawan. I talked with him this past June in Stevens Point, Wisconsin. He has had some success on 10% saline systems were he was experimenting with quinos. Not sure how to get ahold of him, but he probably has more info on this subject, then anyone I know.

You will need everything that you would put on a reef tank for an aquarium. In salt water you don't want lose organic proteins in the water, so you need a protein skimmer aside from normal aquaponic setup. I would also suggest a calcium reactor to make keeping your calcium and magnesium easier to control on that large of a system and a UV sterilizer to control algae. Also remember that some algaes release something called allelopathy which is basically toxins to kill there neighbors that must be neutralized occasionally with something like chemipure or purigen. What questions do you have specifically about your proposed system. This has peaked my interested and i can very much help you.

I plan to build commerical saltwater aquaponics in south NJ, did you already run such system successfully?

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