Aquaponic Gardening

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Hey everyone,

I have some plants growing in my AP system and they just don't seem to be doing that well. After reading through some posts on here i decided that i should check some water quality characteristics besides the basic ammonia, nitrate, nitrite, pH stuff. I figured a nutrient deficiency could be best approximated with hardness and alkalinity, and sure enough they are both pretty low. So how do i correct this issue without raising my pH. Currently my pH is in the mid to high sixes, which is right were i am trying to keep it. I supplement water replenishment almost soley from rain collection. So my system is definitely lacking in nutrients. Everything that i see about adding nutrients usually is in conjunction with raising the pH. So it there a way to supplement nutrients without raising the pH or do i supplement and then correct pH.


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Well, changing the hardness of your water is really like taking a shot in the dark as far as nutrients are concerned. If your plants aren't doing well, it's best to find out what they really need. Look at the symptoms. Yellowing leaves? Green veins? Old leaves dying? New leaves dying?

Got any recent pictures?

I'm more interested in what things i could use to improve the nutrient content. Not necessarily looking to adjust hardness or alkalinity. I just understand that a nutrient deficient water will have low readings on both of those, and since i use almost exclusively rain water to replenish my tanks its a fair bet that my plants are going to need some help.

here are some pics of what i have growing:

These are some sunflowers i planted back in february, they looked great until and nice little rainstorm blew the lids right off my tanks and took them out today. They grew well and had great color.

My spinach is a little different. They just don't seem to be doing that well. Now they are in my DWC setup and all the plants in there aren't doing so well. I need to redo my overflow positioning so that the pipes hold less water to give the roots better aeration.

However when you compare those to some peas i have growing there are some similarities. Notice the yellowing in the lower leaves and the dying off of some of the ones at the bottom.

So even though the flood and drain beds are better i am getting similar results.

Next are some lettuce plants which look good but the leaves have a bitter aftertaste and when you pull the leaves off there is a milky "substance" coming from the plant. Which i thought was something that happened to lettuce plants as they got older and where ready to bolt.

So between the rain water supplementation and poor growth on some of my plants i am fairly convinced that my water is lacking essential nutrients, and i am trying to figure out what i can do. I have been adding salt slowly just for the sake of my fish. I have been using pure Himalayan salt because it will help add nutrients as well. To date i haven't even put in a pound yet.

any help would be greatly appreciated.

Hi Sticky, The big problem from our end in terms of helping you is that we have no idea the size of your system so when you say "not even a pound" of salt it means absolutely nothing. In one IBC that would kill everything. In a 20,000 gal system it would be paltry. See my point. Details man.


Thanks for your response, i have about 320 gallon system with 4 flood and drain growbeds (two 50 gal barrels cut in half).

Currently I have less than 100 fish, somewhere between 50 and 70. My water quality is good in terms of the standard 4 metrics, ammonia = 0, nitrites = 0, nitrates =0, and ph between 6.0 - 6.5. right now the pH is a little low and i have ordered some supplies to bring it up (hydrated lime and potassium hydroxide,

I looked up a thread on the salting issue and according to one of the modertators, Vlad it would take 2lbs of salt to affect a 1 ppt change in a 250 gal system. So i am ok with adding 15oz.

I am really looking for some tips, pointers, experiences from other aquapons who have dealt with nutritional deficiencies and how they approached them, and what they used to stabilize their systems. Since I use almost exclusively rain water to keep my water full i know there will be some deficiencies and i want to address them in a manner fitting an AP systems.


For starters I have been using wood ashes to keep the ph up as the bacteria are constantly bringing it down in order to break down the minerals. We use granite so that is rather neutral. The wood ashed are natural in nature and buffer slowly and the bio-char bits are a favorite among the bacteria as well (readily available carbon). Keep in mind that the salt is only used IF you are seeing problems with the fish health. Not good for the plants. I throw in a handfull of plain water softner salt about every 6 mos. but I also use a small dose of colloidal silver every now and then which also keeps things aerobic. You can Google "cs for fish" and learn more about that as well.

As to supplements I have been using Maxicrop with iron that I purchase right here from Sylvia and her price is great. Other than that there is so much going on in mature GBs with earth worms, etc. that we do little else but keep our water quality up with home made filters, etc. and harvest delicious Trout and veggies year round (despite -20F temps this Winter).

BTW until I am convinced otherwise I do everything I can to keep rain water OUT of our system due to the heavy chemtrailing going on now. Look that up as well and you may find an alternative water source, in our case a deep well, more suitable.

The nutrient deficiency issues I've seen with Spinach are a lack of Nitrates (should have at least 25 mg/L) and Iron.  I add Chelated Iron to my system.  You can get it from a local garden store.  I wouldn't add more than a tablespoon at a time, since it binds up oxygen and can lower DO.

I agree Jim, but i am on city water so i am not sure what is worse. Currently my wife and i are trying to buy a piece of property outside of town and then i can switch over to well water and just adjust to that.

thanks for the info.

I some iron and pH buffering additives on order right now. hopefully they will be here this week.

thanks for the input.

Jeremiah Robinson said:

The nutrient deficiency issues I've seen with Spinach are a lack of Nitrates (should have at least 25 mg/L) and Iron.  I add Chelated Iron to my system.  You can get it from a local garden store.  I wouldn't add more than a tablespoon at a time, since it binds up oxygen and can lower DO.

Here's a useful chart: 


Montmorillonite is also a great source of minerals. We often add it to our compost.

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