An aquaponic system merges two agricultural processes, aquaculture (the cultivation of fish) and hydroponics (cultivation of plants without soil).
Fish eat food which creates waste, and this waste is primarily ammonia.
Ammonia must be removed from the system as quickly as possible because ammonia is toxic to the fish.
This is where we introduce the nitrifying bacteria and the plants; good bacteria such as Nitrosomonas spp convert ammonia to nitrates, suitable for plant uptake.
Nitrates are food for plants, but they are toxic to the fish in significant amounts.
So, before the fish are added, we need to cycle the system. Cycling is the process that converts ammonia to nitrates through nitrifying bacteria.
We Discover: You will have a wait time before adding fish. Will you need to wait for plants as well, or can they be added at the time you set up the aquaponics system?
How Long Do You Need to Wait Before Planting in Aquaponics?
Plants rely on the waste created by the fish to grow.
So to add the plants in my opinion the best time to introduce them is after you feel comfortable that your cycling is complete, and the fish are eating and producing waste.
By the time you are comfortable cycling will happen have allowed for the bacteria colony to grow enough to sustain the system. The cycling process takes about four to six weeks.
If your plants are begin to show signs of stressed growth, you may want to consider adding more fish or create more bacteria. The later can happen by adding some commercial culture from your local aquaponics products store.
This option could affect your organic only claim, if your system is going to be considered for an organic only method.
For Example: Some farmers will just introduce the plants into aquaponics right when they get their system setup. The fish are not available when they are introducing plants because the fish will be provide fertilizer during the initial planting. They will add the organic supplements needed for the initial nitrogen cycle.
Introducing Plants to an Aquaponics System
Introducing plants to an aquaponics system is pretty much like planting in a soil garden.
There are several ways of adding plants to aquaponics.
These are:
- Direct sowing
- Using starter plugs
- Cloning
- Transplanting from nursery
Direct Sowing
This approach involves placing the plant seeds directly in the grow bed.
It is suitable for a media bed aquaponic system because inserting the seed in the media bed requires just a hole to be made, the seed placed in, and the fill media used to cover the seed.
The seed will be supported by the pebbles, gravel, baked clay, etc., as it grows from seed to seedling.
To directly sow a seed, the best way is to sprinkle the seeds evenly across the media bed and lightly cover with media directly after.
It would be necessary to push larger seeds deeper into the media where it would be moister, because it’s necessary for the hard seed coat to soak rather than let the seed germinate.
Also, be sure to sow densely, to account for poor germination. After you see germination, you can thin as needed.
Final thought: seedlings that are crowded will grow poorly and develop weak stems and weak leaves. Direct sowing is good for green leafy vegetables and herbs.
Using Starter Plugs
This is one of the best methods to introduce sensitive plants in your aquaponics.
Some seeds are difficult to germinate, and once some grow into seedlings, they will be weak seedlings that will not hold their own.
Starter plugs are cup-like structures filled with media and you will add the seeds into separate starter plugs and wait.
Once they germinate, you will transfer the starter plugs into the media bed, make a hole in the media, and place the seedling along with the starter plug and cover it with media.
Common starter plugs would be:
- rock wool
- paper towels
- and peat
Starter plugs are suitable for any new plant including peppers, tomatoes, and eggplants.
Cloning
Just like in soil, certain plants can produce seedlings from a cut stem inserted into the growing medium.
This simply involves taking a cut in-stem from a mature plant, and inserting it into the growing medium.
This method is not possible for every plant, but herbs such as mint and basil do produce roots from the cut stem.
Additionally, you can increase rooting speed by adding rooting stimulants; these are hormones that promote the process of roots establishing from the stem.
In this process, you enclose the hormones in a containers; you dip the ends of the stem into the hormone before inserting the stems into the growing medium.
Transplanting from a Nursery
Transplanting is one of the earliest sowing procedures with many benefits.
The process involves sowing seeds in a separate garden/nursery, then you wait until the seeds germinate into strong seedlings that you can transplant to the media bed.
In the soil, the abundance of nutrients and adequate sunlight will speed up their germination and growth.
It is particularly important when you are happy with the root and shoot system of the plant to remove the seedlings from the soil and carefully rinse away all of the soil.
Then you can place the new plants deep in the grow media so that roots have easy access to moisture.
Works Fine: You can also apply the rooting stimulator before transferring the plant and dipping it in the media to help soothe the roots that might have been damaged in the process of transplanting.
Conclusion
In an aquaponics system, plants rely on the waste that fish excrete to grow.
That waste will be converted to nitrates which are ready to be absorbed by the plants through the action of a group of bacteria called nitrifying bacteria.
This means that you should consider the cycle complete before you add your plants to the aquaponics system.
Typically, the cycle will take four to six weeks to complete.