System not working

sammied

I am currently living in Haiti running an orphanage. I am in the midst of setting up an aquaponics system. We have 40 talapia and 150 gallons of water. We have a grow-bed that is 2ft x 6ft x 10in—roughly 12 sq. ft. total. Our water is pumped by a 12v pump, fills the grow-bed in about 20 minutes and has a bell-siphon to send the water back to the fish. The grow-bed contains clay bricks that were broken up into approx. ¾ inch rocks. (We had to use this media because all of our stone here is full of lime.)

The ammonia level is at .25 ppm, the nitrite level is at 0 ppm and the nitrate level is between 80 & 160 ppm. Our ph level is 8.2+ (our reader only goes up to 8.2). We can’t seem to get anything to grow. We have tried tomatoes, basil, oregano, lettuce, cucumbers, watermelon, peas, etc.

We aren’t sure if the reason our plans are not growing is because of the current temperature (90 degrees Fahrenheit during the day), the media we used in the grow-beds, the amount of sun they have, or something we cannot even detect. We do not have access to chemicals to boost the numbers, it is something we have to do in a natural way. Any help or suggestions would be much appreciated.

arbe

Some pics of the plants would help members of the forum help you.

My guess will be your pH. Is the media neutral? What is your source water like?

sammied

The source water ph was 7.4 the last time we checked it. We believe that the media is neutral, however we aren't entirely sure how to check it. We just came up with an idea today to put some rock in a container (that won't effect the ph) and wait a couple of days to see what kind of ph we end up with.

We will take some pictures tomorrow and put them up.

nosliwmas

Hi sammied,

sammied wrote:

We believe that the media is neutral, however we aren't entirely sure how to check it. We just came up with an idea today to put some rock in a container (that won't effect the ph) and wait a couple of days to see what kind of ph we end up with.

Alkaline media is easy to check with vinegar. I tested 3 gravel samples that I could source locally by filling up a clear drinking glass halfway with each of the samples. Then I filled each of the glasses with vinegar. One of the glasses started bubbling -- not much, just a little, kind of like an old soda pop might do after being left out for hours. That gravel had a limestone component and was visually whitish. So the vinegar test ruled out using that gravel due to its alkaline nature. Maybe that method would be easy to try?

--
Sam

sammied

Sam, we tested the brick with vinegar like you suggested and sure enough, it has lime in it of some sort... But then after about 20 minutes it stopped bubbling. Does this mean that we have something alkaline on the outside of our stones? What would you all suggest for equalizing the system back out/cleaning the rocks?

Asia-Off-Grid

If you can get any, I wonder if some pH Down would help, at least temporarily until you could find a different grow media?

ebeuerle

Do you have access to river rock/pebbles? Might be a better choice over brick...

SeanD

Were the bricks recycled? Any chance there is still some mortar/cement/concrete attached to them?

This will push your pH right up

nosliwmas

sammied,

I am gearing up for building ferrocement growbeds -- I made some practice ferrocement planters this weekend. Jajaja... I think I need a lot more practice before I tackle growbeds, but I'm hard-headed and a quick study. My next practice ferrocement projects I'm sure will be less wasteful and I'll be able to build things much faster. But I have yet to find a good fish-safe sealer I can use, so I'm currently planning to try doing a series of acid-baths to chemically get rid of the high alkalinity that a cement surface will surely have. Something like this described on the Fish Channel as a way of curing a cement pond and making it fish-safe:

Concrete ponds can be "cured" and made safe for fish without any special coatings

Maybe doing some sort of similar acid soak of your media will knock the pH down enough to help?

--
Sam

Petesake

I did maintenance in brick manufacturing plants and the biggest cause of decay was the liberation of sulfur from the drying and cooking process of the bricks. Bricks being porous could absorb water and release a form of sulfuric acid in which not much will live.

sammied

Here is a picture of our system. We have 2 fish tanks and one settling tank (far left). We have approx. 40 fish and 150 gal. of water.

We removed the clay brick rocks and put them in a separate area to test our theory that the rocks were causing the higher ph. However since we have done that, the water in the 50 gal drums keeps rising. We've used Muratic acid to lower it, but the next day it is right back up to 8.2. We have yet to get it below 7.8 ph. The stone however seems to be reacting to the muratic acid better than the fish water, staying low for longer periods of time but still not what we want to see.

Also want to reiterate that we are living in Haiti. We have the system built under the eaves of our house to protect it from the harsh direct sunlight. It gets sun approx. 2-3 hours a day during the late afternoon. Also, the water heater that looks like it is sitting on the settling tank is not related to our system... Its just our shower water heater...

ebeuerle

Where's the grow bed? I suspect the high pH coupled with the high temp outside is making it hard to grow anything that is a cool weather plant(lettuce, most leafy greens etc.). Since it's a newly cycled system, it will be hard to grow tomatoes, cucumbers without a lower pH. I would just try and run the system with leafy greens that are more tolerate to warmer temps until the temps come down, then switch to cooler weather greens since it should be starting to cool off a bit as fall is finally here. Over time, the pH will drop naturally.

Do you have access to insulation foam? A DWC might be easier since you are having a hard time finding pH neutral grow rocks but you will have to build some additional filtration...

dlf_perth

Quote:

I would just try and run the system with leafy greens that are more tolerate to warmer temps until the temps come down, then switch to cooler weather greens since it should be starting to cool off a bit as fall is finally here.

+1 Eddie

might be out of your diet scope but Asian greens go well in hot humid weather in an AP.
Pak Choy, Bok Choy, Chinese Broccoli, Asian Cucumber etc etc

Pumpkin (would have to be managed)

you could also try water cress etc. And some of the tropical vegetables
Kangkong, loofah etc. Few ideas here http://www.tropicalpermaculture.com/tro ... ables.html though would have to sort out the ones that will be OK in an AP setup.

>> It gets sun approx. 2-3 hours a day during the late afternoon.

also wonder about your light situation. Most plants need a full day of filtered sun in those sort of conditions.
(so under a shade cloth or green-house type material)

>> try doing a series of acid-baths to chemically get rid of the high alkalinity that a cement surface will surely have.

That may work. Use you muriatic acid (or simply get hydrochloric acid which is same thing and sometimes cheaper under that label) and soak the bricks in an acid bath for 24 hours or so.

sammied

We have taken everything down to the bare roots and found that our water is what is causing the issue. We stuck the water in a bowl and monitored the ph and within 8 hours it went up .4. How on earth does water continue to go up in ph when there is nothing in it?

ebeuerle

CO2 out-gassing is the usual culprit - if the water has a bunch of carbonates in the water but water has dissolved CO2 and after sitting for a while the CO2 leaves and the pH will rise in response to it's "true" pH level.

This usually happens with water from wells. Where is your water from?

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