How To Grow Lettuce In Aquaponics

How To Grow Lettuce In Aquaponics

One of the benefits of having your own aquaponics system at home is that it allows you to grow food for your own consumption and, if taken into a bigger scale, even sell some of the fresh produce. Popular plant choices that are easily cultivated using the system include herbs like mint and leafy vegetables like lettuce since they are easy to maintain and have no complicated nutrient requirements.

You can easily grow lettuce in an aquaponic system using a variety of methods such as through grow beds, nutrient film technique, or deep water culture. It can be grown from seeds to seedlings and planted to floating boards and PVC pipes with a typical growth time of 24 to 32 days. 

Ideal conditions to grow lettuce in aquaponics   

If you’re just starting out with the aquaponics system it’s natural to experience some failures along the way. While lettuce is easy to grow with the system, it still needs the ideal conditions to grow and flourish. 

Here is some vital information on the best conditions for growing lettuce:

pH level 

The recommended ph level for lettuce is between 5.8 and 6.2 although it may survive beyond this range and will benefit from higher calcium level in the water to prevent tip burns in the leaves during summertime. 

Water and air 

The desired water temperature for lettuce is between 70 and 74 degrees Fahrenheit or 21 to 23 degrees Centigrade. It is also a good temperature for most fish used for the system. Be sure to maintain the airflow in the grow room to increase nutrient uptake and transpiration. 

Plant space 

For the best yield try to maintain plant space by planting lettuce 7 inches apart as it encourages maximum growth and prevents overcrowding and from blocking the light. However, the rocket lettuce variety needs less space compared to the butterhead variety. The best types of lettuce varieties that grow well in an aquaponics system include the loose-leaf, romaine, and butterhead. 

Even though plants in an aquaponics system is less prone to pests, it can still exist and attack your cultivated plants like lettuce. To prevent pestilence, try to put predator bugs or ladybugs that eat pests without harming the lettuce. You can also place a bug net over the lettuce to protect it from pests.  

Methods used 

These are the best methods to use in growing lettuce because they provide the easiest approach especially if you’re just starting with aquaponics. 

1. Floating raft or deep water culture (DWC) 

This method utilizes rafts made of polystyerene that easily float on water and involves a permanent supply of water. Lettuce seeds are placed in individual holes and the roots hang in oxygenated water. Once the seedlings are in place, you only have to monitor the growth and schedule transplanting at least once to allow proper spacing. 

2. Growbeds

Compared to the earlier method, lettuce roots in grow beds won’t sit in the water all the time and there are bell siphons that handle the drain cycle allowing the lettuce to have the nutrients, water, and oxygen they require. Rockwool is the best option for the seed starter cubes. 

How to grow lettuce in aquaponics?

Here are the basic things that you need if you want to grow lettuce in aquaponics using the raft system:

  • plant spacing of 18 to 30 cm 
  • growth time is 24 to 32 days 
  • a temperature of 15 to 22 degrees Centigrade 
  • plant height  is typically 20 to 30 cm 
  • plant width is typically 25 to 35 cm 

Basic materials needed

  • tank – any clean container that can accommodate 10 or more gallons of water or if you only have a small system an aquarium may also be used
  • raft – styrofoam sheet about one inch in thickness 
  • under gravel filter and pump – a pump is used to pull the water through the gravel to promote biofiltration and air hose tubing is needed as two-way gang valve 
  • aquarium gravel- it’s used so as not to leach the water that could lead to changes in the pH level. 
  • pH test kit – to ensure that the pH levels are maintained 
  • growing medium – these are usually Rockwool or oasis cubes which are seed starting mediums to get the plants started
  • siphon cleaner – it’s used for monthly tank maintenance 
  • light source – the setup should be near a sunny window but artificial lights are also needed for at least 16 hours to help the plants grow 

Instructions on how to grow lettuce in aquaponics 

Lettuce seeds are ready for transplant at three weeks when the plants have 2 or 3 true leaves. A phosphorus supplement may be added in the second or third week to prevent stress during the transplanting period. 

If you’re transplanting lettuce in a colder climate be sure to expose the seedlings to the colder temperature and to direct sunlight for at least 3 to 5 days for more probability of survival. If transplanting in warm weather be sure to put a sun-shade over the plants to avoid water stress for at least 2 to 3 days. 

Always maintain a high nitrate level in the system to have crisp and sweet lettuce and if you’re cultivating them in growbeds, see to it that there are taller plants alongside to partially shade them. Recommended fish match for lettuce includes tilapia, trout, bass, sunfish, koi, and carp. 


Growing lettuce in an aquaponics system is considerably easy to maintain and just make sure to check the pH level every week. A pH of 6.8 is ideal but it if to goes beyond 7 then the pH should be adjusted using pH Up and Down liquid solution. Make sure to fill the tank with de-chlorinated water to top off the level and each month vacuum the excess waste out of the gravel with a siphon cleaner. For this process, the tank water level should be down to ¼ but don’t throw the water down the drain as it’s good for indoor and outdoor plants. Finally, fill the tank again with de-chlorinated water. 


You can already harvest lettuce in just 28 days and if you notice that the heads and leaves are large enough for consumption.  Be sure to harvest it early in the morning while the leaves are moist and crisp and chill it immediately so that the freshness will be maintained. 

How long does it take for lettuce to grow in aquaponics?

It takes an estimated time of 28 to 30 days for lettuce to grow in an aquaponics system but you can already harvest it as soon as it reaches the desired size. There are, however, some more rare lettuce varieties require at least 8 weeks before it can be harvested.