Help! Aquaponics Garden pH Too High - Need Advice!

In summary, the first attempt at building an aquaponics garden resulted in swapped water and a pH change. The second attempt, using more accurate tests and a water conditioner, resulted in high ammonia levels.
  • #1
mcstatz5829
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TL;DR Summary
Could increase from 0 to 4ppm ammonia increase pH from 7.4 to 8.2?
Hi everyone, hoping for some quick help.

I’m trying to get the chemistry right for an aquaponics garden I’m building. I screwed up pretty bad the first time and just swapped out almost 100% of the water (there was a residual 2-3 gallons in the bottom of the growbed).

Last night added in about 60 gallons of filtered drinking water. Tested the pH at 7.4. When I tested the pH, I don’t think there was enough time for the 2-3 gallons in the growbed to fully mix in.

Last thing before bed was adding some urea to decompose into ammonia.

This morning pH was 8.2! And ppm ammonia was 4.

What I don’t know:
Buffer of the water (suspecting weak)
pH of the residual water (prior tests were 7.2-7.4, but I believe the water was brackish and the tests inaccurate. Freshwater aquarium testing kit used).
Prior ppm ammonia (assumed 0, water was straight from tap filter)

I’ve read urine tends to be acidic, but I’m guessing that changes as the urea decomposes into ammonia?

What I’m trying to hopefully understand is if the majority of that 8.2 pH is because of the ammonia, which would be good, or if pH will stay elevated when the ammonia is converted to nitrites, which would be bad.
 
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  • #2
This is tricky, for many reasons. The simplest approach says that 4 ppm ammonia means around 2×10-4 M*, assuming nothing else is present such a solution would have pH of around 9.7. Any buffers present will make the change lower, but at least there is no doubt ammonia can't be ruled out as a reason behind the pH change.

* I believe kits check the presence of ammonia and ignore ammonium ion, so the total concentration of both forms would be around ten times higher.
 
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  • #3
Thanks! That's exactly what I needed to know.

I did some googling over lunch and was able to convert to molarity (assuming pure ammonia solution) and came up with something similar. Been over 10 years since I've been in a chemistry course.

Interesting if the test kits only include NH3 and not NH4+. Maybe only the NH3 is toxic to fish?
 
  • #4
Partially that, but making a test that will react with both can be challenging. Once you know pH and concentration of either ammonia or ammonium ion (doesn't matter which one), calculating the other is trivial.
 
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  • #5
Do you know if water conditioner can throw off the tests?

I'm in Indiana with very hard water and my city uses chloramine. First go at this, I filled up from the tap and used a water conditioner designed to remove the chloramine/chlorine.

I then used the tank to urinate in for a week straight. Ammonia levels didn't budge. I added 10% ammonium hydroxide, and ammonia levels barely budget even after a full gallon in a 150 gallon tank. The greenhouse stank of ammonia but it only got to 4 ppm.Fast forward to round two. I used a drinking water filter that removes chloramine. Had to lug 5 gallon buckets to the greenhouse and back and only got it halfway filled right now after 3 hours yesterday. Urinated in it twice, and already I have ammonia levels high off the scale (8+ ppm)

Good news is the tank is only half full, so I can dilute it down (3 more hours of lugging water...)
 

1. Why is the pH level in my aquaponics garden too high?

The pH level in your aquaponics garden may be too high due to a variety of factors, such as inadequate water flow, overfeeding of fish, or excessive use of alkaline materials in the system. It is important to identify the root cause in order to effectively address the issue.

2. How does a high pH level affect my aquaponics garden?

A high pH level can have a negative impact on your aquaponics garden as it can disrupt the balance of nutrients and bacteria in the system. This can result in poor plant growth, stressed fish, and an overall decline in the health of your garden.

3. What can I do to lower the pH level in my aquaponics garden?

There are several steps you can take to lower the pH level in your aquaponics garden. These include adding acidic materials such as vinegar or citric acid, increasing water flow, and reducing the amount of fish food. It is important to monitor the pH level regularly to ensure it stays within a healthy range.

4. Can I use chemical pH adjusters in my aquaponics garden?

While chemical pH adjusters may provide a quick fix, they can have negative long-term effects on the health of your aquaponics garden. It is best to use natural methods to lower the pH level, such as adding organic acids or increasing water flow.

5. How can I prevent the pH level from becoming too high in the future?

To prevent a high pH level in your aquaponics garden, it is important to maintain a healthy balance in the system. This includes regularly testing and monitoring the pH level, avoiding overfeeding of fish, and using natural methods to adjust the pH level when needed. It is also important to regularly clean and maintain the system to prevent any buildup of alkaline materials.

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