Stuppy Aquaponics Blog

Are the fish supplying enough nutrients to the aquaponics system?

Posted by Conor Quinlan on Jan 31, 2017 9:04:28 AM

 

 

Nitrogen (mg/L)

 

 

 

Date

pH

Total Ammonia

Ammonia

Nitrite

Nitrate

Temp (Fo)

Alkalinity

mg/L

EC (mS)

01/20/16

7.8

0.25

Neg.

0

50

80

55

0.81

1/24/17

7.58

0.25

Neg.

0

55

73.4

55

0.83

1/25/17

7.5

0.25

Neg.

0

55

74.6

-

0.84

1/27/17

7.7

0.25

Neg.

0

50

74

60

0.82

01/25/17  -> Total Hardness: 205 mg/L CaCO3 equ

Calcium Level: 35-40 mg/L            Magnesium level: ~26 mg/L

Phosphate Level: ~3 mg/L (as PO4-)

 

By: Conor Quinlan

Water Quality Overview: Water quality is maintaining well and steadily nitrate levels are rising but it’s still not at a significant level. The arugula in the float bed is likely keeping levels more constant. pH is starting to be more affected by nitrification which is gaining momentum as more waste is produced and the feeding ratio goes up. pH is still fairly high though and until the pH drops to 7 ideal crop growth cannot occur; this is another reason why light feeders like arugula are used when starting the system and why its recommended to start fish between 10-50 grams and not less. The build-up of nitrifying bacteria has proven to be more than rapid enough to sustain transformation of waste from fish, in a newly reset system, at >10 grams in size.

fish tank after restart.jpg

Fish Update: The fish are maintaining well with no deaths due to their environment. Although the fish are growing they are not growing as rapidly as last week’s measurement depicted which isn’t too surprising since the data showed the fish weight nearly doubled in a week. Therefore, the average last week was likely to high an estimate as the larger fish can be easier to catch sometimes. This week’s average increased from 7.92 g -> 9.06 g an increase of only 1.14 g versus last weeks estimated increase of nearly 3.9 g. This is why weekly averages are calculated, in order to use the data in the future to determine a growth rate relationship that’s more accurate. So far the fish have increased from an average of around 1 gram to over 9 grams (9x increase) in 37 days using a feeding rate around 7.5-8% body weight.

Crop Update: Tomato crops in the media bed have finally begun to fall over due to their height and brittle stems. Unfortunately, the increase in nitrate and other nutrients that has occurred over the last month have not been sufficient enough to improve the tomato growth. The extra iron is improving the young growth quality but the lower leaf sets have completely died off at this point.

tomato comparison old water vs new.jpg

A third tray of arugula was seeded on 01/19 and the second tray (seeded on 01/09) was added to the float bed following the staggered production method of growing.

staggered arugula production.jpg

The first tray of arugula, seeded on 12/30, has sprouted several sets of leaves at this point that appear to be of fairly high quality. New foliage looks very green and therefore nutrient conditions are high enough to maintain the quality of this light feeding crop. Other light feeding crops such as herbs like oregano and parsley and specific fruiting bodies like peas and beans may also be grown fairly well at these lower nutrient levels during system start up.

Because of the rapid growth of light feeding crops and the rapid accumulation of nitrifying bacteria (established only 10 days after the restart of the system) we have seen in our research only 7-10 days of waiting time is required before adequate nitrate is available for light feeding crops with fish 10 grams or greater. Essentially 10 days after the fish are placed in the system crops can be effectively supported by the nutrients that become rapidly available by nitrifying bacteria. 

Bucket Testing Station: There is a lot of data to process that could provide some very interesting information pertaining to the relationship between water quality and crop physiology. This round turned out to be a good trial and error test for the upcoming experiment which will be with tomatoes again. However, this time the various changes that were implemented throughout the last experiments such as adding pH and EC measurements and tracking acid additions, will be used from the start enabling more accurate results.

I will be comparing aquaponics and hydroponic based solutions side by side to observe any differences in crop quality. I will also be comparing water quality EC and pH of each solution to see if any correlations exist between nutrient uptake and different water quality parameters. Various supplements can also be added to the aquaponics based tomato crops to directly compare aquaponic solutions with different nutrient contents.

tomatoes in bucket testing system.jpg

Above is an image of the tomato test buckets (the middle bucket is hydroponic and the outer two aquaponic) The aquaponic grow tomatoes show greener foliage and a little purpling on the undersides of the top leaves (characteristic of a light phosphorous deficiency)

artichoke flower.jpg

Above is an image of the artichoke flowering, this flower is the artichoke heart.

System Update: An improved NFT prototype for our aqueduct system is being built in our research area. This NFT system will represent what are product will actual look like when it is released within a month. These channels will have lids that allow easy cleaning and root removal and provide a lot more space for root growth enabling crops to grow as large as possible. The smaller holes keep light from penetrating into the channels keeping algae from growing and our gutter will simply slip onto the end of the channels allowing for their easy removal and spacing customizability between 8”-12” spacing depending on the crop being grown. Below is an image of the system nearly completed.

New NFT mock-up.jpg

 

Topics: Aquaponics, Aqueduct Development, Plants, Water, Fish