Growing Aquaponic Tomatoes

Aquaponic systems are designed to grow fish in a water tank and use organic plants, such as tomatoes, to filter and clean the water that is being circulated for the fish.

The tomatoes get their nutrients from natural “fertilizer” that the fish provide in the tank water. Once you get your aquaponics system to achieve biological balance, then planting and growing your tomatoes is a relatively straight forward process. It is very much like planting an organic tomato garden, and many of the same principles apply here.

Growing organic tomatoes has the main advantage of producing and harvesting more vegetables than with traditional growing methods. You will find that the aquaponic tomatoes grow much quicker using the nutrient film technique, and that the end result will be tastier and juicier tomatoes that you will delight in harvesting.

The steps to get your tomatoes growing quickly in your system are as follows:

1. Purchase your organic tomato seedlings from an organic grower or from a local market. You can raise the tomato plants to seedlings yourself if you like, but make sure that the seeds that you use are organic. As with any other crops that you decide to plant in an aquaponics system, do not use pesticides, herbicides, insecticides, or dangerous fertilizers with the organic tomato seedlings.

Using an equal parts mixture of sulfur powder, cornstarch and talcum powder is an excellent natural way to keep the rodents and pests away from your seedlings.


2. Decide which media you will use to grow the organic tomatoes in. The best medium should be pH neutral (7.0), provides adequate support for the tomatoes, has good moisture retention properties, and has decent spacing for proper air exchange. Clay pellets, rockwool, and coconut fiber make excellent choices for most growers.

3. Insert your stakes into the media. The best choices are usually wood or food-grade plastic stakes, as they are environmentally friendly. You can help to support your tomato plants by using ties that are connected to the outer edges of the grow beds.

I like to also lay a metal screen flat over the aquaponic media surface, which can be used to anchor the tomato stakes in the upright position. If you can not find a suitable metal screen to use, you can use chicken wire as an excellent alternative. You can place spacers under the edges of the screen or wire as needed to raise it as the seedlings grow.

Just ties the stakes to the screen or chicken wire, and if you need additional support, consider suspending ropes or nets from a frame to support the quick growing tomato plants.

4. Using a pH test kit, check the acidity of the media and the water being circulated from the fish holding tank. Usually, I like to grow organic tomatoes in a system with a pH ranging from 6.0 to 7.2. You can use pH Up/pH Down to adjust the conditions if you need to. If your aquaponics system is in biological balance, you should not have to make large adjustments, but sometimes the media can change the pH a bit.

5. Once you have a stable pH level, transplant the tomato seedlings into the grow beds. Be sure to use the clay pellets or perlite to make a thin layer of media that will cover the root ball of the tomato seedlings. This will help provide moisture to the roots, and will prevent them from drying out.

If you are planting the seedlings in compost or a heavier aquaponics media with good moisture retention, this step will not be necessary. In either case, you do not want to have too much media covering the root ball, since this could result in promoting root rot, and will effectively suffocate the top roots by not allowing them the oxygen that they need. A thin layer is all you need.

6. Add some red wigglers (also known as earthworms) to the media you are using. The earthworms will provide additional fertilizer and minerals that the organic tomatoes will use as food. Additionally, the worms can help to provide more oxygen in areas where the roots might be suffocated in the aquaponic media.

7. After the seedlings have been transplanted into the media for about 4 to 6 weeks, check the phosphorous levels of the fish holding tank water and growing media. The tomatoes should be close to blooming, and phosphorous is important for their health at this time. If levels are low, add aquatic organic fertilizer to the media at the recommended rates on the package.