Backyard Aquaponics
A place to discuss aquaponics

Yep, the nitrogen cycle is alive and well in the ocean just as much as in freshwater.


Haven't got a reference for that have you Rupe ? Not questioning, just wann read a little more !

Download from here CD... http://aem.asm.org/cgi/reprint/64/1/258

There's also a list of references included in the article I wrote for BYAP mag #5.... email me if you want the whole article and list of references...

Good morning Rup et al.

Having sorted out that the bacteria can be as effective in a marine environment as freshwater, how would a system be set up to run a growbed system to grow a salt tolerant plant species.
I could see that the medium could become encrusted with salt through evaporation and there would be other practical problems.

Are there any references to setting up a sea water AP system .?

WD

I think you will have a considerable cost in supplying the salt, because you'll need to replicate all the trace minerals too Unless your pumping straight from the sea?

The only trials I've seen grew "ulva".... a type of seaweed... sometimes called sea lettuce... apparantly in high demand in Asia...

I've heard of posibilities of salt bush... and something else that I can't remember at the moment...

Ulva is lovely I eat it all the time

Freoboy

Pumping straight from the sea was the original query and the thing that gave us the most problems such as (a) how do you get sufficient ammonia from the caged fish to convert to useful nitrate for the plants and b) what effect the salt water would have on the bacteria etc, etc.
Being a nuts and bolts man I found it difficult to conjure up in my mind how you would set up a useful system.

WD.

I think you could do a net search on the University of the Virgin Islands, Marine Biology section, on the Fish and Fauna they study. They have a large lab that is run off of a constant flow from the Ocean, which fills all their tanks and just overflow to return to the Ocean. I know they study all the marine critters that live there and some of the plants but I don't know which ones. They do all the studies without feeding other than what comes out of the Ocean there. I did not know anything about this stuff when I lived there. I just saw the people in town some times and was warned about scuba diving in their lab areas. """NO TOUCHING AND NO DISTURBING ANYTHING INSIDE THERE MARKED PLOTS OF STUDY!!!! PLEASE""""" was the warning the dive shops gave everyone who dived there.
There plots would be a simple square maybe 3 or 4 foot with 2 foot tall stakes with a string tied around at the top so stuff could get in and out. If a starfish or a sea urchin or any thing else went through they monitored it and studied it but did not disturb it.

I forgot I wanted to ask if there is a chart here for plants that still thrive at 3ppt salt levels with out changing there taste and flavor. I killed a bunch of strawberries at 3ppt and more. I ate one and it tasted bad.

Do many of your run your systems salted all the time to 3ppt? How does that effect the plants?
I think Ocean is 6ppt.

I believe most plants do ok with up to 3 ppt of salt. There are some notable plants that don't tolerate much salt at all and strawberries is one of them (of course a high pH will also tend to cause strawberries to struggle too.) I believe I noticed that my sweet potatoes did struggle if I salted my system but I don't think it ever killed them, just shriveled a few leaves.

At the moment I'm not thinking of any other plants I've grown that have had any problems with salt levels of 3 ppt but I haven't necessarily grown a huge variety of plants through all seasons while also changing salt levels so I may not know.

When people start looking for very salt tolerant plants they are probably talking about plants that will handle the range between 3-6 ppt which might be needed if one has an ick problem in a system that already has 3 ppt and they need a 3ppt change to treat but this only works with salt tolerant fish too.

I've heard that tomatoes are fairly salt tolerant though at higher salt levels you might not need to add any salt to them when you eat them. (hearsay as I don't actually eat fresh tomatoes myself.) Lets see, I think beets and purslane are also listed as salt tolerant along with saltbush. I'm not thinking of any others at the moment.

Now when you talk about seawater aquaponics, well what was posted above back in April is the most I've heard of anything actually with seawater.

Sea water[ocean] is arount 35 ppt

Hi all and TCLynx
being a n00bie (as my kids tell me!) to all this and doing my research I notice from many of the photos of the plants that some of them look salt affected. There are some interesting trends with certain vegies doing exceptionally well and others just not going at all or very poorly (particularly the cucurbits). As I am intending on putting salt in my system I thought I would chase up some info.
the Department of Agriculture here in WA has a leaflet http://www.agric.wa.gov.au/objtwr/imported_assets/content/lwe/water/irr/f07199.pdf on salt tolerant plants. Interestingly once you get into the 1.5ppt to 3.5ppt (270 to 635mS/m) there are less vegetables that will tolerate those levels of salt and would you know it is the beets (including silver beet) and spinach. Ring any bells? Seems to me they are probably 2 of the more successful crops in aquaponics. From this article it would seem that we should keep the water around 0.5 to 1ppt if we are going to compromise between fish and plant health. If we need to medicate with salt then an investment in a hospital tank would be a good idea.

I appreciate that there is almost certainly a significant difference in the impact salt water has on plants growing in soil and aquaponics but the relativities between the tolerances of plants is what we should be looking at.
Perhaps if we start at 0.5ppt and slowly increase the concentration of salt until the least tolerant plants show signs of damage then stop.

Perhaps someone out there would like to try it out. It would be great to get some hard data on salt tolerance as salting the water and its negative impact on the plants we grow (that are needed to remove the nutrients from the water) is something we could easily overlook as we try to to do what is best for the fish.

my system is starting up in a couple of weeks and I will start the salt at 0.5ppt and work up over summer and see how the veggies react. I'll make sure I have a few canaries (onions, celery and squash) in the mix to give me the early indication that I may be reaching the limit.

Anyhow some thoughts to add to the mix.

Cheers
Marc

and some more info from Alberta (Canada) http://www1.agric.gov.ab.ca/$department/deptdocs.nsf/all/agdex3303

And to top off the night here is a great article from NSW Primary industries on salt tolerance in vegetables and the yield reduction caused by salt water. http://www.dpi.nsw.gov.au/agriculture/resources/soils/salinity/crops/tolerance-irrigated
note 1 dS/m = 1000 EC (or µS/cm) = approximately 640 mg/kg (or ppm) divide PPM by 1000 to get ppt.

for example rockmelons have a 10% drop in production if the salt content of the irrigated water goes from 0.9ppt to 1.5ppt. Also the relativities in this table are different to the other 2 articles I mentioned earlier, so there are other factors in play.
Cheers
Marc