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PostPosted: Feb 21st, '15, 07:36 
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I've been reading this forum some time and have started building a system.

I've buried and insulated an ibc put an inc grow bed on top in the same insulated envelope. My hope is to get it cycled in the spring and winterized before next winter. I would like to eventually expand the grow beds for warm weather and shut all uninsulated beds dkown in the winter.

Right now I'm being held up by subfreezing trmperatures which are not conducive to collecting rainwater.

Anyone have experience with having a portion of their growbed a be seasonal?


I'll post pics as soon as I can figure out how from my old iphone


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PostPosted: Feb 21st, '15, 10:50 
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PostPosted: Mar 1st, '15, 19:39 
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Slow going because of weather and new baby but i just need to add water and media and pretty it up.

It's supposed to be above freezing so I'm going to start filling rain barrels.


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PostPosted: Mar 15th, '15, 09:52 
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Time to get some goldfish and start cycling

Anyone know why I see ammonia in fresh cold rainwater?

Am I fool to start cycling with water at 50 degrees F (10 C) or should I just wait?


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PostPosted: Mar 17th, '15, 10:29 
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Some nutrient questions, if anyone is even reading this:

I am using rainwater, which has low dissolved solids and I am worried that the water will not have enough pH buffering capacity. Therefore, I started trying to figure out what to add. Here's what I've come up with. Any thoughts/comments are appreciated.

The rainwater is pH of around 5.0 (based on a cheap hydroponics color-matching test kit). I've read that aquaponics systems tend to get more acidic with time (makes sense to me that the system is effectively converting ammonia (base) to nitric acid). Therefore, I'm not too worried that I will need to force pH down with an acid.

Based on the quantities of the Hoagland solution used in hydroponics (not that I've ever done that either), I would make the following 'plant food' mix ('parts' given in molar quantities):
2 parts MgS04 (from epsom salt)
1 part KH2PO4 (MKP - note this is a weak acid)
enough CaOH to make the solution only slightly acidic (say between 6 and 7)

Since this mix is potassium deficient, I would add some combination of the following to get 3 parts total of potassium:
KNO3 - if I want more nitrate
K2SO4 - if I don't want more nitrates.
KOH - if I want to push pH higher and/or don't want to add sulfate or nitrate
KCl - Would I ever want to add this if I'm growing strawberries?


My plan is to make a stock solution and just add a small amount to makeup water (e.g., to 10 ppm phosphate perhaps). My thinking is that this will keep plants from being deficient in anything.

I would then control pH by additions of CaOH. If I ever need to push pH down, I think I would add a little food-grade phosphoric acid.

I'll also add a small amount of maxicrop for micronutrients.

I have enough chemistry knowledge to be dangerous. I think this would make a decent buffer solution (stable, resistant to sudden pH changes) and nothing I've read indicate any of my ingredients would be harmful to anything in the system. What I don't know are the following:

Is this worth the effort or should I just react to changes as they happen? One benefit with this approach is that I could start growing plants while the system cycles.

If I add K2SO4, that's alot of sulfates (since I also have MgSO4). Does anyone know at least a ballpark sulfate concentration that is harmful to plants or fish?

Finally, how much Cl is too much for strawberries? Are they sensitive to sodium, chloride, both, or just general ionic strength?

Does the benefits of "salting" come from one particular ion (e.g., Na or Cl) or just a general increase in ionic concentration?

In my scheme, I'm essentially relying on a phosphate buffer system. If I wanted more buffering capacity, I could add more potassium phosphate. Anyone know if excess phosphate is a problem? I've only read that it's a problem for algae but my system is well shaded (fish tank is covered and in-ground.

Thanks to anyone that takes time to read/respond.

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PostPosted: Mar 17th, '15, 12:04 
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A lot of what you said is over my head. Either that or I am beat.

First, plant now. Don't wait to cycle to plan. If you can keep your plants from freezing if you get more cold, plant and let them start. They may struggle a little but they will be in and using some of the nitrates, etc.

I've been told that strawberries don't like salt so I have refused to salt my system because we grow a lot of strawberries.

Since I am not knowledgeable on creating a buffered solution I don't go there. I react to what I see and test for. Sometimes I probably miss the boat, but my goal is simplicity and trying not to add too much to the system.

You said your pH was 5 using the test kit. The APi test kit only goes down to 6 so are you sure you are at 5? If so, there are ways to buffer it up to mid 6's and then see what happens. You can also use some tap water, just let it offgas for a while. For a pH adjustments (I am always trying to bring it down), I treat my top up water and then add that to the tank.

Keep being patient and it will come.


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PostPosted: Mar 17th, '15, 12:26 
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I can't help with your questions but I like your system.
Are the purple sheets an insulating board?

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PostPosted: Mar 17th, '15, 16:05 
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Thanks for the replys.

I used this test kit, which is cheap and goes down to ph of 4.
http://generalhydroponics.com/site/inde ... _test_kit/

The pink/purple stuff is insulation. My plan is to cover the front with an insulated door and the top with a greenhouse plastic dome by next winter but I think I have a couple more weeks until the weather is warm enought to plant. Based on your suggestion I may direct sow a few greens just to see what happens.

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PostPosted: Mar 17th, '15, 23:17 
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Hi Scott,
You would only need to salt for two reasons: 1. stressed fish due to high levels of nitrites or 2. outbreak of fish disease like ich. I would highly recommend fishless cycling and then you wouldn't need to salt. Strawberries are suppose to be okay up to about 1 ppt of salt although I haven't tried growing strawberries yet.

I would add enough calcium and potassium (usually in 2:1 ratio) and small amount of magnesium to buffer the water to around 6.5. Also be careful about adjusting pH too fast as plants, bacteria and fish can't handle large swings.

In regards to your question about salting, it's the chloride that competes with the nitrite in fish to prevent brown blood disease, but like I mentioned before, if you fishless cycle you are unlikely to need to salt.

Plants need very little phosphorus (unless heavy fruiting) and you will get plenty from the fish food so I would focus more on the calcium/potassium to handle the buffering duties. It takes very little to supplement when dealing with heavy fruiting plants.

Hope that helps!

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PostPosted: Mar 18th, '15, 06:40 
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What anion do you add with the calcium potassium and magnesium. The only ones that provide buffering capacity are

Phosphate but the issue is that calcium phosphate isn't very soluble
Sulfate only buffers at lower ph not useful here.
Bicarbonate buffers at higher ph than desirable.
Chloride doesn't provide much of a buffer and plants don't use it
Hydroxide simple but can only use to increase ph
Organic such as citrate or ascorbate. One of these might work but I've seen cautionary words on this forum like citrate is antibacterial.

Since i have so many questions, I'll probably just get a couple cheap things on hand like hydrated lime and play it by ear.

As an update, I added a little maxicrop And fish emulsion yesterday and ph is now 6.8, up from 5. While this is a good pH, This is a big swing for one capful in 1000 L.

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PostPosted: Mar 18th, '15, 08:04 
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I don't typically have to supplement calcium due to the high content in my well water but I would probably use hydroxide. My well water is 7.8 so I usually top up with it and add organic potash to increase potassium. In my much larger system which is under construction I will need to use with ro or rain water but our pH is usually around 7 for rain. You sound like you know much more on the chemistry than I. Is there just a plain calcium carbonate as opposed to calcium bicarbonate?

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PostPosted: Mar 18th, '15, 08:24 
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Calcium comes commonly as carbonate. The problem with carbonate (and bicarbonate) is that it will very effectively buffer your solution around ph of around 8. This buffer is what keeps your blood ph balanced. I would avoid carbonate and add calcium hydroxide, which is commonly available as hydrated lime. This will add calcium and increase the ph but not buffer the ph at a high value.

Calcium nitrate would also work, if you wanted to add excess nitrate without affecting ph. Calcium chloride would leave ph unaffected but add chloride.

While I don't exactly, I think most forms of calcium phosphate and calcium sulfate are insoluble.

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PostPosted: Mar 25th, '15, 23:24 
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Planted some lettuce seed and bare root strawberries.
Put in 20 feeder goldfish.

Chemistry is stable but water is cold. Fish just hide in bottom corner.


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PostPosted: Apr 19th, '15, 04:22 
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Been a bit since I've posted so this will be a bit long.

Bought a few more feeder goldfish. Water temp is up to low 60's. Chemistry still the same. Low levels of ammonia but no nitrate or nitrate.

I built a cover with PVC to keep anyone from falling in. The structure is 4' steel rebar that is inside of 1/2" pvc pipe. Fortunately, the 4' rebar comes the same size as the width of the ibc so no need to cut the steel. The cover should allow me to feed without opening even if I decide to lock it shut one day.

I made an airlift water circulator/filter. Very simple, low-power air pump (3w, 7.8L/m). I think the photo explains it. I put a mesh bag I had on hand at the outlet to catch solids. The pump is inside a similar mesh bag so the plan is that if the solid fits through the mesh, it'll end up in the grow bed. If not, it will end up in my water circulator/filter.

I've added a few teaspoons of some chemicals to feed plants and maintain pH. This includes MPK (lowers and buffers pH), KOH and CaOH (raise pH) and a little iron and epsom salts along with maxicrop. I've added occaisonal small amounts in sum total no more than a couple teaspoons of any one of the chemicals (except about a cup of maxicrop).

I'll add another post with photos (they're on iphone, which I don't like typing on).

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PostPosted: Apr 19th, '15, 04:28 
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