Stuppy Aquaponics Blog

System Update: Frasier 1/9/18

Posted by Conor Quinlan on Jan 9, 2018, 2:30:00 PM

Frasier

 

Nitrogen (mg/L)

 

 

Date

pH

Total Ammonia

Ammonia

Nitrite

Nitrate

Temp (Fo)

EC (mS)

12/6

6.45 ->7.2

0

N/A

0

190 mg/l

75

1.26

12/13

6.75

0

 

0

-

65, 72

1.38

12/20

5.8 -> 7.02

0.5

 

0

-

66,77

1.52

12/23

6.5 -> 7.2

0

 

0

-

-

1.60

1/02

6.0 -> 7.1

0.5

 

0

-

57, 64.5

1.90

1/05

6.6

0

 

0

NEW Lab Sample

71.5

1.88

Media bed_1.jpg

Above is what the media bed and float bed looked like before harvesting on 12/20. Both snap peas and beans grow exceptionally well within the Aqueduct’s media bed and are recommended for use in the curriculum. Below is an image of the media bed and float bed with the new seedlings on 1/02 (seeded 12/20). Nutrient accumulation has been allowed to build up during this seedling stage allowing for greater absorption for heavy feeding crops in the near future.

Media bed_2.jpg

Water Quality

pH fluctuations are allowing for greater additions of the carbonate compound K2CO3, which has increased the concentration of K since the last lab test. The fluctuation has sometimes been extreme bringing the pH to as low as 5.8. This causes an increase in the ammonia concentration as the nitrying bacteria cannot function well at pH’s below 6.5. Between 100-150 gram K2CO3 has been required since the lab test on 12/20 and has been required on a near weekly basis. K2CO3 will need to be replaced by Mg and Ca carbonate based compounds to keep K from competing with cation based nutrient uptake. High K levels potentiate Mn deficiencies, given their similar charge, and have led to slight deficiencies observed in several string beans crops.

Super triple phosphate (STP), Micro Mix, Chelated Iron and MnSO4 have been added this month on 1/02 to speed up the production process. The following amounts of nutrients were added to the system the last month:

STP -> 100 grams, Chelated Iron -> 75 grams, MnSO4 -> 50 grams, Micro Mix -> 15 grams.

The values above have been increased since last month’s addition, notably Mn. These additions have helped increase the EC quickly. Below are the results of the lab sample taken on 12/06:

Parameter

Conc. (ppm)
(8/22)

Conc. (ppm)

10/27

Conc. (ppm)

12/06

E.C.

1.53

0.86

1.16

Ca

64

39.06

42.31

Mg

79.5

34.19

42.84

Na

148.31

73.57

86.19

Cl

98.68

47.76

57.83

B

0.51

0.32

0.48

Fe

6.15

3.53

4.31

Mn

0.08

0.03

0.04

S

138.65

67.79

81.11

Cu

0.46

0.43

0.59

Zn

2.35

0.81

1.22

Mo

0.23

0

0

NO3-N

29.53

26.98

43

NH4

1.18

3.26

0.97

PO4-P

10.58

8.6

13.53

K

28.34

25.48

97.04

The results above show there are several key nutrients that are having an impact on water quality conditions. The negative issues are results of low quality source water and high sodium feed which we currently use to run the system. Our 3.5mm catfish feed has a lower sodium content and has shown to produce lower sodium accumulation over time.

Positives:

Nitrate – As the fingerling have grown in size they have produced a large amount of ammonia based waste which has been converted into nitrate by the nitrifying bacteria in the media bed. This increase has put nitrate level at the lower end of the ideal range for aggressive vegetative growth.

Phosphate – Very important for fruiting crops, phosphate levels don’t need to be nearly as high as nitrate and potassium; in fact, very little P is required for the successful growth of leafy green and vegetative based crops within aquaponics. However, flower development and root growth rate is greatly affected by P concentrations, therefore when root growth is minimal it could be due to very low phosphorous levels.

Potassium – Probably the single most important nutrient for most fruiting crops, potassium is required in the highest concentration by varieties such as tomatoes, cucumbers and peppers. Higher levels of potassium are obtained from the compound K2CO3 which is added to buffer pH as well as add large doses of K. Thanks to the ideal water and air temperatures the pH has consistently decreased over time requiring regular carbonate additions. This will be useful for the growth of heavy feeding cold season crops that will be seeded in the near future, such as Brussel sprouts and cabbage varieties.

Negatives:

Sodium – Sourced from both the tap water and fingerling fish feed. The feed is the primary cause of higher sodium levels over time but decreases when it is changed to the 3.5 mm size catfish feed which is prepared with a lower sodium content. Some few crops, mainly light feeding herbs like oregano and thyme, cannot be seeded at these concentrations. It is recommended to seed crops in a small germination station outside the system with pure water when Na is >100 ppm before transplanting into the system.

Manganese (Mn) – Mn can often be sourced directly from the water being used, nut unfortunately our tap water doesn’t contain sufficient levels of dissolved Mn. While MnSO4 does appear to add some Mn to the solution it is very minimal due to the compounds lower solubility at higher pHs. For this reason, double the amount of MnSO4 (50 grams) was added during the most recent addition.

The higher temperatures during the summer months caused pH to remain consistently high, lowering carbonate addition required. Lower temperatures over the winter, coupled with inline water heating, has led to the appropriate pH response of decreasing overtime. This is due to the water temperature staying within a more ideal range for the nitrifying bacteria. Based on experimentation and observations in the summer and winter it is clear that clogging is far more likely to occur when the water temperature is EITHER higher or lower than the ideal range of between 70-78 F.

A water sample was taken on 1/05 for JR laboratories and will be discussed in the next update.

Fish Update:

The last fish weighing was taken on 12/23 before the holiday break and each fish weighed an average of 100 grams, up 20 grams compared with what they were two weeks before. According to our fish growing schedule the tilapia are slightly above where they should be in terms of size, while being lower in anticipated feeding rate. The fish were fed a max of 145 grams of feed per day before weighing, according to the tilapia grow schedule they should require 180 grams per day at their current size.

Water temps are falling further below the ideal level due to the low air temperatures in the warehouse and therefore the feeding rate had to be further decreased from the max of 156 grams per day, set after weighing, to a minimum of 120 grams per day. Whether this will affect the growth rate of the tilapia will be determined during the next weighing.

Despite the low feeding rate, the fish are of adequate size to switch over to the 3.5mm catfish feed starting next week.  

 

Crop Update:

The entire system has been filled with new cold season crops. The float beds contain both iceberg and green/red cabbage varieties while the media bed contains more string bean and snap pea varieties. This time far more snap peas were seeded as they were found to take up far less space than the beans.

The crops are growing but unfortunately the thrip infestation came back over the holidays and nearly destroyed all the new seedlings. The area was treated with neem oil before seeding but thrips have been known to survive below the surface of media and given the cold air environment I wouldn’t be surprised if the thrips find this preferable, making them even more difficult to kill off. I have switched the natural pesticide to a pyrethrum/sulfur mix which is known for being fairly potent but is proving to be less effective than anticipated. The crops will continue to be sprayed until the infestation is depleted and other crops surrounding the area will be treated with the mix as well to help ensure they do not spread. If the mix doesn’t kill the thrips within the next week or two, a new pesticide will need to be sourced.

Brussel sprouts will be one of the large crops seeded in the media bed next as the cooler temps are ideal for their production. String beans and snap peas will continue to be seeded as well.

Topics: Aquaponics, Water, Pest Management, Frasier, Aquaponic Supplements, Potassium