If there’s one plant you should grow in aquaponics, it’s lettuce!
And why lettuce exactly? Well, out of all the aquaponic veggies, lettuce is the easiest and most sought after! It has multiple varieties, it grows extremely fast, it’s forgiving of beginner mistakes, and most importantly, it’s flat-out delicious!
But, as with any aquaponic vegetable, there’s still a pretty big learning curve (and it may be steeper than you think). So whether you’re an aquaponic beginner or an established grower, read this guide, get comfortable with the information, and build up your lettuce-growing skills!
Table of Contents
- Growing Conditions
- Aquaponic Lettuce Facts
- How to Grow and Harvest Aquaponic Lettuce
- Pairing Lettuce with Fish
- Lettuce in NFT Systems
- Lettuce in Media Beds
- Lettuce in Deep Water Culture (DWC)
- Lettuce Varieties
- Aquaponic Lettuce Advantages
- Aquaponic Lettuce Disadvantages
Growing Conditions
- pH: 6 to 7
- Ideal pH: 5.8 to 6.2
- Temperature: 59 to 72 F (15 to 22 C)
- Plant Spacing: 18 to 30 cm apart
- Germination: 3 to 7 days in temperatures between 55 and 70 F (13 to 21 C)
- Harvest Time: Between 24 and 32 days but certain varieties can take longer
- Light Exposure: Full sun with slight shading in warmer temperatures
- Plant Height Maturity: 20 to 30 cm
- Plant Width Maturity: 25 to 35 cm
- Recommended Aquaponic System: DWC, NFT, Media Bed
Aquaponic Lettuce Facts
- Lettuce is a high-demand, high-value vegetable
- Great for both home growers and commercial growers alike
- Lettuce is a winter crop and enjoys cool temperatures
- Lettuce has a low nutrient demand (making it great for aquaponic systems)
- Head growth favors air temperatures of 3 to 12 C at night and 17 to 28 C during the day
- Water temperatures over 26 C will cause lettuce to “bolt” and become bitter
- Summer lettuce crops favor higher calcium concentrations to prevent tip burn
How to Grow Lettuce in Aquaponics
As lettuce is a low-nutrient, high-demand vegetable, it’s a perfect plant for first-time growers and those trying to get their feet wet. But that doesn’t necessarily make it a cakewalk either! Before you get started, make sure you fully understand the ins and outs as it’ll save you a lot of time when it comes time to grow!
Here’s everything you need to do to grow lettuce effectively in aquaponics!
Step 1: Lettuce Germination
Lettuce should take between 3 to 7 days to germinate in temperatures between 55 and 70 F (13 to 21 C). If you’re new to aquaponics and your curious as to what goes into the germination process, try reading our “Seeds and Seedlings” guide to learn more.
Or, if you’re wanting some assistance getting started, it wouldn’t hurt to check out some starter kits on Amazon such as the MIXC Seedling Trays (with humidity dome), the NEWKITS Starter Tray Kit (with humidity dome), or the SOLIGT Seed Starter Kit with Grow Light.
Step 2: Transplant Your Seedlings
Once your lettuce seedlings are about three weeks old and have 2 to 3 true leaves, it’s safe to transplant them into your aquaponic unit.
But before you officially transfer them over, try giving them a little extra phosphorous in the second or third week. This will give them a little more root growth and will “harden” the plants so they’re not stressed.
Additionally, if you’re growing outside, try gradually exposing your lettuce seedlings to normal growing conditions — such as colder temperatures and direct sunlight — 3 to 5 days before you officially transplant them. This should give them plenty of time to adjust to the elements.
Step 3: General Maintenance
Lettuce maintenance is pretty easy (at least compared to something like cauliflower) and it shouldn’t take a lot of effort on your end. Your five main responsibilities are:
- Keeping the lettuce roots aerated (exposing roots to an adequate amount of oxygen)
- Providing an adequate amount of lighting (10 to 18 hours should suffice depending on variety)
- Maintaining your water quality (easier to do once your system is well-established)
- Inspecting your system periodically for leaks, durability, algae growth, etc.
- Keeping your fish alive and healthy (try reading our “Fish Health and Disease” guide to learn more)
Step 4: Harvest Your Aquaponic Lettuce
Depending on the variety of lettuce you’re growing, you have two options when it comes time to harvest:
Cut and Come Again: when the plant reaches a size you deem acceptable for consumption (doesn’t have to be full maturity), you can start cutting/harvesting the outer leaves (popular with loose leaf varieties and romaine). As the plant grows, the leaves you cut off will eventually be replaced.
Whole Head: when the plant reaches maturity or a size you deem acceptable for consumption, you can cut at the base of the plant and harvest the entire head of lettuce (popular with iceberg, bib, and romaine lettuce).
Pairing Lettuce with Fish
“Fish to Plant” pairings are important in aquaponics, yes, but you shouldn’t overthink it either. If you see something that suggests that lettuce can “only” be grown with one kind of fish — such as trout — that’s incorrect.
While a cool-weather plant like lettuce will do well with a cold-weather fish like trout, that doesn’t mean that lettuce and trout should always go together. In fact, when it comes to fish pairings, it’s better to go with a fish that’s tried, tested, and hardy. One that’s been proven to work well in aquaponic systems and one that will tolerate your mistakes.
So bottom line up front, put just as much emphasis on “fish suitability” as you do on “matching temperatures.” If you’d like to learn more and explore your options, try reading our “Best Fish for Aquaponics” guide.
Lettuce in Nutrient Film Technique (NFT) Systems
NFT systems are perfect for growing lettuce and should let you grow just about anything (minus some of the heavier lettuce varieties). For NFT systems, your plants will sit on top of a “channel-like tube” (think of a gutter downspout) and dangle their roots inside the chamber. And your lettuce roots, which are freely hanging, will soak up nutrients from the “film” of water and nutrients that moves through the bottom of the tube.
The three main advantages of growing lettuce in NFT systems include:
- Allows for vertical stacking
- Least amount of water needed (comparatively)
- Minimal labor needed to maintain and harvest
For a full breakdown of NFT systems, try reading our “3 Main Types of Aquaponic Systems” guide or our “6 Types of Hydroponic Systems” Guide to learn more.
Lettuce in Media Beds
Out of all of the aquaponic systems, media beds are the most popular with hobbyists. They’re efficient with space, have a relatively low startup cost, and are very forgiving of beginner mistakes.
In effective hobby systems, your lettuce will sit within a grow area (that’s covered in a growing media such as coco coir) and be periodically flooded. The rise and fall of the water will expose your lettuce to the perfect amount of nutrients and oxygen.
The three main advantages of growing lettuce in Media Beds include:
- Easy to master if you’re a lettuce-growing beginner
- Simple design and fairly forgiving
- All lettuce varieties can be grown (including heavier types)
For a full breakdown of media bed systems, try reading our “3 Main Types of Aquaponic Systems” guide or our “6 Types of Hydroponic Systems” Guide to learn more.
Lettuce in Deep Water Culture
In aquaponics, Deep Water Culture (also known as the “raft system”) involves a sheet of Styrofoam that floats on top of water. Holes are cut within the Styrofoam and your plants (aka your lettuce) will sit within each hole (using a net pot and growing media) and dangle/submerge their roots into the water below.
The three main advantages of growing lettuce in DWC include:
- Great for larger setups with a singular crop like lettuce (may be difficult for small-scale aquaponics)
- Easy to observe your lettuce roots (simply pick up the raft)
- Spacing can be easily adjusted to fit any lettuce variety (simply change out the raft and cut new holes)
For a full breakdown of DWC systems, try reading our “3 Main Types of Aquaponic Systems” guide or our “6 Types of Hydroponic Systems” Guide to learn more.
Lettuce Varieties in Aquaponics
There are many varieties of lettuce that can be grown in aquaponics, but for the purposes of this article, we’ll look at 4 general types: Iceberg lettuce, butterhead lettuce, romaine lettuce, and loose leaf lettuce.
1. Iceberg (crisphead) Lettuce
- Description: A round, cabbage-like type of lettuce with pale-green leaves that wrap around the plant
- Taste: Mild and sweet taste that’s crispy and crunchy
- Climate: Prefers cooler climates
- Harvesting: Harvest the whole head of lettuce
- Aquaponic System: Any system but best for DWC or Media Beds
- Difficulty: Easy but can be difficult to get the head formation correct
2. Butterhead Lettuce
- Description: Cabbage-like in appearance with soft leaves
- Taste: Soft and buttery taste with very little crunch
- Climate: Prefers cooler climates
- Harvesting: Harvest whole head or cut-and-come-again
- Aquaponic System: Any system but best for NFT
- Difficulty: Fairly easy to grow, maintain, and harvest
3. Romaine Lettuce
- Description: Tightly folded leaves that sit upright and
- Taste: Mild and sweet with a slight crunch to it (not quite as much as iceberg)
- Climate: Prefers cooler climates but can tolerate some heat before bolting
- Harvesting: Cut-and-come-again or whole head harvesting
- Aquaponic System: Any system will grow romaine effectively
- Difficulty: One of the easier types to grow but will take time
4. Loose Leaf Lettuce
- Description: Loose leaves that are piled on top of each other (several varieties)
- Taste: Mild and sweet flavor with less crunch
- Climate: Prefers cooler climates
- Harvesting: Cut and come again
- Aquaponic System: Any aquaponic system will work great
- Difficulty: One of the easiest types to grow in aquaponic systems
Advantages of Growing Lettuce in Aquaponics
- Lettuce is one of the best plants to grow in aquaponics and can be grown in every type of system
- Lettuce grows faster, larger, and healthier in aquaponics
- It’s an overall cleaner process and you don’t have to deal with soil
- Lettuce can be grown inside or outside
- Easy to avoid pests since growing without soil
- Aquaponic lettuce is a great beginner vegetable and is forgiving of rookie mistakes
Disadvantages of Growing Lettuce in Aquaponics
- Growing lettuce aquaponically can have a high startup cost (compared to growing in soil)
- Even though lettuce is an easy plant to grow in aquaponics, it can still be intimidating if you’re a beginner
- Lettuce may have difficulty growing in newer setups (best to let your fish and system run for 3 months before adding any lettuce in).