Mini aquaponics system

By: Sophia Shelton (farm intern)

Have you ever had a pet fish? Did you ever think that your fish could be used to grow plants? Well, it can, by aquaponics!

Aquaponics is when you use fish and their waste to give nutrients to the plants you are growing with just water, hydroponically.

I started my internship at FoodChain in August 2021. When I started, they gave me a mini aquaponics system. I was told to use this for research to help them know what they should do or change when giving the systems to younger kids. The system came with a tank, a light, food, water quality tests, a fish, an airstone, and seeds.

Starting a mini system:

I started my tank by growing cilantro on August 23. Everything was normal. My water quality was good and my fish seemed to be doing ok. I noticed that he wasn’t eating. I saw him eat for the first time on September 6th. He has been swimming normally and not acting weird. The cilantro was growing well too. I saw sprouts about a week or so after I started the tank. By September 2nd, the cilantro had really grown a lot!

The cilantro kept growing, but it was all stem and barely any leaf. It was also very tall and falling over. I asked the farm manager why this was happening and she said that the plants are basically reaching for the light. So, I trimmed the stems down and moved the light down closer to the plant. Since then, I haven’t noticed the cilantro growing very much and the tops of the plant almost look dead. My water quality is still normal.

Since the water quality was normal, and nothing seemed wrong with the tank or fish, I asked the farm manager what to do. She told me that since the plant hasn’t grown any since I trimmed it and the tips were burnt, that I should just go ahead and start over. Once I started over, it took a few weeks for the cilantro to start growing again. Within a couple of days the cilantro had grown pretty tall. The water started getting really green, so I did a water exchange. To do a water exchange, you remove ⅔ of the water and fill the tank back up with water. The plant still has a lot of stem and not a lot of leaf.

In a mini system like this, the most important water quality measurements to check for are: pH, Nitrite, Nitrate, and Ammonia. Below you can see the measurements for the system since I set it up.

Date	pH	Nitrite	Nitrate	Ammonia
8/23	7.0	.3	10	.5
8/25	7.0	.3	10	.5
8/26	7.2	.3	10	.5
8/29	6.8	.3	10	.5
9/2	7.0	.3	10	.3
9/4	7.0	.3	10	.3
9/6	7.0	.3	10	.3
9/10	7.0	.3	10	.3
9/14	6.8	.3	10	.3
9/17	6.8	.3	10	.3
9/20	6.8	.3	10	.3
9/22	6.8	.3	10	0
9/27	6.8	.3	15	0
9/29	6.8	.3	15	0
10/3	6.5	.3	15	.3
10/11	6.8	.3	30	.3
10/14	6.5	0	10	0
10/17	6.8	0	0	0
10/20	6.8	0	0	.3
10/22	6.8	0	0	0
10/25	6.8	0	0	.3
10/27	6.8	0	0	.3
10/29	6.8	0	0	.3
10/31	6.8	0	0	.3
11/2	6.8	0	0	.3
11/4	6.6	0	0	.3
11/6	6.8	0	0	.3
11/9	6.8	0	0	.3
11/11	6.8	0	0	0
11/13	6.8	0	0	0
11/15	6.8	0	0	.3
11/17	6.8	0	0	.3
11/19	6.8	0	0	.3
11/21	6.8	0	0	.3
11/23	6.8	0	0	.3
11/25	6.8	0	0	.3
11/28	6.5	0	0	.3
11/29	6.2	0	0	.3

Check back for more updates as I continue experimenting with the mini system!