Grow: Foolproof Hydroponic Gardening in a Tub
If you think hydroponic gardening is difficult or expensive – you’re wrong! A simple tub (or even a milk jug) and a handful of easy-to-find (and cheap) products and you can hack yourself a hydroponics garden.
I wanted to title this post “The Easiest Hydroponics Ever” or “Set It and Forget It Method” or “No Excuses Growing Method”. But Tub Hydroponics seems to be the most accurate name for it.
Basically we are going to show you how to turn this collection of things:
into these fabulous looking leafy vegetables.
Anyone who knows me well, understands I really enjoy Aquaponics. I love how everything works together forming a complete cycle. I feed the fish, the fish provide nutrients for the bacteria which convert it into food for the plants which in turn provide me with food. When functioning correctly it is truly a beautiful thing. Aquaponics is a very big and complex subject. So big that I didn’t want our first real grow something post diving into the depths of Aquaponics. I had to find something simpler.
Well, if we remove the fish and bacteria from the system we are left with Hydroponics. I provide nutrients in a circulating water system which feeds the plants and the plants feed me. Normally when growing things hydroponically we need to have big discussion around reservoirs, water pumps, air pumps and nutrient solution. And, oh yeah, lighting, salt build up, pH adjustments, constant monitoring, nutrient solution additions and replacements and so on and so on. It’s a discussion that quickly boggles the mind, causing it to shutdown and go huddle in the corner like a stressed out parakeet. Same thing happens when I talk to my kids about cleaning their room, but I digress.
Still too complex. There’s got to be a way to make it easier, simpler. Think man think! How about removing the pumps and just make it plants, water and nutrients. Time for some Google research! Bingo! Found a link to “Three Non-Circulating Hydroponic Methods for Growing Lettuce” by B.A. Kratky from the University of Hawaii.
The basic premise is very simple. Fill a container full of nutrient rich water and cover with a lid. Place a lettuce seedling in a special pot called a net pot and place it in a hole in the lid such that the bottom of the pot is touching the water. The seedling gets water from the container, likes what it tastes and sends out more roots to get more of that nutrient rich water. The plant continues to grow, sends out more roots and consumes more water. A moist air gap is created between the surface of the water and the bottom of the net cup. In this gap the plant sends out smaller horizontal roots to absorb oxygen. Kratky refers to these roots as “oxygen roots”. If you were to fill the air gap with water it would drown the plant.
So what does all that mean to us? It means simple, easy, set it and forget it lettuce in a tub. Or what I like to call Tub Hydroponics.
Let’s get started.
First gather your materials:
- 1 – 7 gallon tube with lid
- 4 – 2 inch net pots
- Rapid Rooter grow plugs
- Some lettuce seeds
- Hydroponic fertilizer
- A small plastic tray
- A 2 inch hole saw
- And some water
A note about tubs: Not all tubs are created equally. See this tub I bought from a local home improvement store.
It has a nice locking lid with blue handles. Perfect size, not to pricey. All looked good till I got home and looked at the locking handles a little closer. I realized they drilled holes through the side of the tub to secure the handles. When I compared the net cup to where the holes were, it became apparent when filled with water up to the holes, the bottom of the net cup would not be in water.
I therefore recommend simple restaurant bus tubs with lids. They are perfect for this application. I bought mine from the Food Service Warehouse for a little over $9 for tub and lid. Also tubs that are too deep will not be able to maintain their shape when adding larger amounts of water. Look for the ones that are approximately 7 inches tall. Avoid clear tubs as they will allow too much light into the reservoir which will lead to algae growth. Algae Growth = Bad News.
So let’s get on with it!
Step 1 – Prepare Your Tubs
Take your 2 inch hole saw and cut four evenly spaced holes in your lid.
I used the ribs on the lid as a guide.
Take a utility knife to remove the little bits of plastic left by the hole saw.
Set you lid and tub aside for now. Also sneak that hole saw back before someone notices it’s missing and you didn’t ask permission to use it.
Step 2 – Plant Your Seeds
Take four moist Rapid Rooter plugs and place them in your four net cups. If the Rapid Rooter plugs are not moist you can soak them in some water for a minute or two.
Take a fifth plug (I used an old dry one) and break it into four pieces. Slide one piece in each cup to hold the full plug steady.
Place two leafy greens seeds in each of the full rapid rooter plug holes. If the hole is not open, you can open it with a tip of a pencil.
Place your four net cups in a shallow tray and fill the tray with a quarter inch of water.
Cover your tray with a thick dish cloth and put it in a dark place till the seeds sprout.
After two to three days, move your seedlings into the light and refill water to the quarter inch mark.
On the seventh or eighth day remove one of the seedlings by pinching or cutting it off so each net pot has a single plant in it.
By the end of 2 weeks your baby plants should look like this.
Step 3 – Fill Your Tub
Take an empty net cup and place it in one of the holes in your lid. Put your lid on the tub and fill the tub with water till a quarter of an inch of water is visible in the bottom of the cup.
If you are using a tub other than a 7 gallon tub, you will need to determine how much water you have in the container. A 7 gallon tube will be hold approximately 5 gallons of water when filled to the appropriate level. To determine the water volume take the lid off and measure the approximate width, height and depth of the water.
*** Warning Math Ahead ***
Multiply all three measurements together.
Ours was 18″ long, 14″ wide and 5″ deep.
18 x 14 x 5 = 1260 cubic inches
Convert to cubic feet by dividing by 1728.
1260 cubic inches / 1728 = 0.729 cubic feet
One cubic foot holds 7.48 gallons of water, so multiply by 7.48.
0.729 cubic feet x 7.48 = 5.4 gallons
Step 4 – Add Nutrients to Water
Next you will need to add the Nutrients to the water. I am using a mixture of a Tomato Master Blend, Calcium Nitrate, and Magnesium Sulfate (aka Epson Salt) in the following ratios:
- 2 grams of Master Blend per gallon of water
- 2 grams of Calcium Nitrate per gallon of water
- 1 gram of Magnesium Sulfate per gallon of water
You can check out MHPgardener’s video explaining the ratios. He has had great success using this mixture.
Pour nutrients into the tub and mix with your hand. It will take some time to dissolve. It is ok if a little settles on the bottom.
Step 5 – Check pH of Water
Use a pH testing kit to check the pH of your water and nutrient solution. The ideal range will be between 6.4 and 6.7. If you use rain water, typically adding the nutrients will result in a pH in the ideal range. If the pH of the water is high, you can add a few drops of lemon juice, mix and retest again. Or you can use a hydroponic pH lowering solution. The good news is, once you test your water and determine what is needed to adjust it to the ideal range, you will not need to retest in the future. Just add the same amounts of pH adjusters.
Step 6 – Insert Seedlings
Place the lid back on the tub and drop the seedling filled net cups into the holes we made in Step 1.
Step 7 – Wait
Place your tube where there is a good deal of light. I recommend natural sunlight, but they can be grown under full spectrum fluorescent tube lights (6500K). And then wait. Leave it alone. Don’t touch it. Don’t add any water. Just let them grow.
This is the first day in the sun for these guys.
By the beginning of the second week you should see some substantial growth.
Beginning of week three. Going strong!
Beginning of week four. Almost ready to harvest.
Beginning of week five and these Bok Choy and Tat Choy are ready for harvest.
Here are the roots at 5 weeks. Notice how low the nutrient solution is. Look at the healthy, strong root system. The health of the plant can be determined by the size of the root system.
If you are growing in an area that has light only from one side, you may rotate your tub every few days to encourage even growth. I haven’t had to do this yet.
Step 8 – Harvest and Eat!
Enjoy the fruits of your hands-off tub hydroponics.
Milk Jug Hydroponics
You can even do this in a recycled milk jug! I would stick with a lettuce variety on this method. Things like Bok Choy and Tat Choy are big water consumers.
The changes I made here was the elimination of the net cup. Instead I stuck a toothpick through the very top of the Rapid Rooter plug to hold it in the open top of the gallon jug. I filled the jug to an inch below the top and added enough nutrients for one gallon of water. Capped the jug and shook the jug to mix. Removed the cap and insert the plug in the open lid. Make sure the plug reaches the water level initially. You only need about a quarter of an inch in the water. The let it sit for four to five weeks.
Tub Hydroponics Shopping List
This is the same bus tub I used except it is in white. I think the lighter color would be better for hot sunny climates were over heating can become an issue. Black tubs may work better in cooler climates and indoors where heat absorption would be desireable. The walls on this tub are thick and don’t bulge when filled with water.
The lid for the tub. You could mix and match color’s if you wish. I just choose to keep them all the same color. This lid for the bus tub is solid. It’s designed to stack other bus tubs full of stuff on top. Definitely will hold up the plants without sagging.
These are 2 inch net cups. They should have ample space to allow the roots to grow down through the netting of the cup. I avoid ones with solid bottoms. Also ensure the net cups have a small lip on the top. I ran across a few that did not have a lip and would slip through the hole cut by the hole saw. You can also source these from a local hydroponics store if there is one in your area.
These plugs make seeding simple and easy, but by no means are they required. You may start your seeds any way you wish. Just make sure you have some sort of media that will allow capillary action to water the plants. Rock wool cubes will work well too, but require an extra step of dipping in a low pH solution for 10 seconds or so. If you start your seeds in soil, you will need to wash the soil off the plant’s roots and transfer to a different media for capillary action.
I have linked to some Red Cross Butterhead Lettuce, but you may use any leafy green seed in this system. Adriana and Red Cross are two of our favorites. I suggest some trying all sorts of varieties. Keep in mind what the weather will be like 4-6 weeks from planting your seeds. Some varieties are more heat tolerant while others thrive in cooler temperatures.
This is similar to the Master Blend Tomato Mix I use. It has the same N-P-K ratio and the same mixing instructions. This formula also contains a fair number of trace minerals for plant growth. With the addition of the Calcium Nitrate and Magnesium Sulfate growth resulting from this mix is incredible.
pH Adjusting Kit
Simple but easy Hydroponics pH adjusting kit. It includes a testing solution as well as pH raising and lowering solutions. Getting the pH into the 6.4 – 6.7 range really helps the plant growth. You can also purchase a water testing kit from a pet store to check your pH. Remember though, we are looking for the ideal range after the addition of your plant nutrients.