Stuppy Aquaponics Blog

System Update: Frasier 5/10/17

Posted by Conor Quinlan on May 10, 2017 2:30:00 PM

System #1


Nitrogen (mg/L)






Total Ammonia




Temp (Fo)



EC (mS)




















6.5 to 7.1









6.4 to 7.3








04/24/17 -> Total Hardness: 420 mg/L CaCO3 equ
Calcium Level: 78 mg/L  Magnesium level: ~54.5 mg/L
Phosphate Level: ~ 20 mg/L (as PO4-)


Water Quality Overview:

The pH has finally reached levels low enough to add K2CO3. I have added a total of 150 grams to the system from 5/03 to 5/05 which had a significant effect on the pH but had some unexpected consequences. K levels actually decreased since our most recent lab conducted water quality test from 16.3 mg/L to 14.7 mg/L. The addition of K2CO3 will begin increasing this concentration fairly rapidly.

On 5/03 50 grams of K2CO3 was added to ensure the change in pH and alkalinity was not too extreme. The pH increased from 6.5 -> 7.1 because of the very high solubility of the compound. MgCO3 and CaCO3 are dependent on lower pH for greater solubility where as K2CO3 is not. Upon retesting the system on 5/05 the pH had dropped dramatically to 6.4. This is much faster than expected but 100 g more K2CO3 was added on 5/05. This increased the pH to 7.3. This should retain the pH for a longer period of time with the alkalinity at 50 mg/L. It Is possible that the feeding rate is great enough to substantially increase the effects of nitrification causing the quick drop in pH. On the other hand, this larger addition of K2CO3 will improve K levels for crops. Since there is plenty of Mg and Ca in the source water K2CO3 will be my pH adjusting compound of choice until K levels are sufficient (>150 mg/l). This will allow us to utilize more fruiting crops in our system in the near future.

The most recent laboratory based water quality test was received early this week. Low levels of Mn and Mo were reported, the kelp powder did not add significant levels of these micro nutrients. We have therefore ordered chelated Mn as that is the nutrient causing the most severe deficiency problems. Mo is only required is very small amounts to encourage optimal crop growth. The lab tests currently show none available, so we are hopeful that this will not become a problem. 

P has risen significantly since the addition of super triple phosphate, 1.26 mg/L to 5.83 mg/L, therefore 50 grams per month will continue to be added throughout the life cycle of the system to keep strawberry production and quality high.

Among the more significant problems discovered with the water quality test is the accumulation of sodium in the solution which is becoming toxic to many crops. The two sources of sodium are source water and fish feed. The most significant is the feed. We are currently looking at alternatives that are more ideally suited for aquaponics purposes. 

Fish Update: The tilapia in system #1 are finally eating the appropriate amount of feed for their size and are up to consuming 188 grams/day which is nearly 70 grams greater than the feeding rate on 4/24! This means that the fish are close to weighing about 100 grams each. I am hoping that the higher feeding rate will being adding more micronutrients to the system, particularly Mo which is a difficult micronutrient to source.

Frasier5_10_1.jpgAs you can see the fish tank is getting darker due to the higher feeding rate of the fish. They are difficult to see but have grown substantially. The feeding rate will be kept constant until the water clears some. The darker water is a sign that the fish are at their feeding capacity

Crop Update: The crops are still producing very well and the beans harvested last week were delicious despite a couple nutrient deficiency (mainly Mn and K). Crop quality should increase significantly now with the addition of K2CO3. A couple cups of micronutrient hydroponic blend have been added to the solution to temporarily raise the Mn and Mo levels while more viable fertilizers are found. A chelated Mn powder will be used to raise the levels of this micro nutrient. Mn is definitely causing the most significant deficiency in both bean and strawberry crops and will need to be corrected as soon as possible.


Sodium is turning out to be a significant problem and is likely the cause of previously observed plant growingproblems. The herbs oregano and thyme aren’t growing well and even other crops like swiss chard and spinach appear to be impacted. A test will need to be done to demonstrate the effects of hydroponic solution with reasonably levels of Na compared with the effects of high Na. Many crops remain unaffected by the high sodium levels including the mixed lettuce, strawberries, peas, beans, rosemary and lavender.

The peas are now producing fruits and the strawberries are developing very nicely! Beans are continuing to produce very rapidly as well!  No problems to report here despite the deficiencies observed.


In the image the peas have grown so large that they have to be placed on their sides to keep from hitting the lights. The peas will continue to be wrapped around the PVC poles as they grow.


You can see the dramatic change is strawberry crop size from 4/24 to 5/5. Most of the varieties are bearing fruits and many are already producing side shoots (runners) which produce more individuals. These should be cut in the NFT channels. You can see the Mn deficiency forming slightly on the upper most leaves with a light green color. So far the rest of the crop remains unaffected


 Finally, you can see the strawberry crops beginning to form and the peas are looking exceptionally great. 

Topics: Aquaponics, Fish, Strawberries