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Hydroponic Tubs: A Build-It-Yourself Guide

I've assembled a simple hydroponic grow tub. Here are my tips for getting your own project started.

Learn how to build a hydroponics system with a Rubbermaid tub.

Learn how to build a hydroponics system with a Rubbermaid tub.

Why Build Your Own Hydroponic Growing Tub?

I wanted to build a hydroponic grow tub for so many reasons:

  • I enjoy gardening and growing vegetables, and this was a new way to do it.
  • I am not all that impressed by the quality and price of a lot of the produce at any local grocery store.
  • The fruits of this particular labor are sweet indeed (of course).

Growing fruits and vegetables in a garden or soil work just fine, but I had always wanted to see how a hydroponic system works, so I seized my opportunity this spring. This was a fun and fairly simple project.

Don't get me wrong, there were mistakes made along the way, but overall, it has exceeded expectations. I grew tomatoes and cucumbers. I can't wait to see what pops up the rest of the season!

Things you'll need to turn your Rubbermaid tub into a hydroponic tub.

Things you'll need to turn your Rubbermaid tub into a hydroponic tub.

You'll need to drill holes in your Rubbermaid tub.

You'll need to drill holes in your Rubbermaid tub.

What You Will Need

  • 1 Rubbermaid 18-gallon tub, used as a water reservoir.
  • 1 can of black spray paint, used to block the sunlight.
  • A drill with a 3" bit.
  • An aquarium air pump, for proper aeration of water.
  • An air stone, for some serious air.
  • 25' tubing.
  • 11 net pots, to cradle your plant babies.
  • 1 bag hydroton, pea gravel, or perlite, for stabilizing and a moisture-wicking media.
  • 8+ seedlings.
  • 1 kit nutrient solution to feed your plants.
  • 1 water pH level tester, strips, or digital gauge to maintain proper pH levels.
  • Baking soda and vinegar, for cheaply lowering/raising the pH levels.
  • Several zip ties, to strap things down.
Plant seeds into starter pods.

Plant seeds into starter pods.

Seedling planted in starter pod.

Seedling planted in starter pod.

Plant Seeds About a Week Before You Begin (4 Steps)

  1. Using the starter pods I bought for this hydroponic system, I planted my seeds about a week ahead of this project. Most veggies will germinate and begin to grow root systems in 6-10 days.
  2. The starter pod I bought was not necessarily designed for seed starting, but it worked just fine. For my second tub, I bought the correct pods (General Hydroponics Rapid Rooter plant starters). They worked just as well if not better. I also bought some Spanish moss.
  3. The seedling you see in the picture is a cucumber seedling, and you can see it effectively sprouted and developed a solid root popping straight out of the bottom of the plug. Hydroponic cucumbers tend to shoot up fast. I also have hydroponic watermelon seedlings, which started out shorter and stronger. The hydroponic tomatoes are growing slowly and steadily in these early stages.
  4. Remember to plant extra seeds. You want to over-plan for plant loss due to disease, seeds that don't germinate, or silly mistakes, which you will see happened to me.

Cut Circles, Paint, Then Re-Paint (3 Steps)

Painting the tub black is important so the water in your reservoir does not see the sunlight. Sunlight will spur the growth of algae in your nutrient solution and will only cause problems such as clogging your system and inhibiting all-important root growth.

  1. First, I washed my 18-gallon tub and allowed it to air dry completely.
  2. I then cut out circles on the lid of the tub. I placed my net pots upside down in the arrangement I desired on top of the lid. Using a pencil, I outlined the cups and used the circle cutting bit and the drill to cut nearly perfect 3" circles. The net pots will rest inside these circles. Using a file, I smoothed the insides of the circles, removing the plastic strands left rough by the drill bit.
  3. I then painted (or outsourced to my oldest son :) the outside of the tub thoroughly with black spray paint. Let it dry for 10 minutes, then spray it a second time. Again, don't miss a spot. Sunlight blocking is important, even for indoor hydroponics. Recommendation: At first I used the cheapest black spray paint I could find (.96 cents at Walmart). I highly recommend spending 2 more dollars and getting glossy. It covers quickly, you don't use as much, and it is much better looking.
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The finished tub.

The finished tub.

Wash your balls...hydroton balls, anyway.

Wash your balls...hydroton balls, anyway.

Fill tub with water about 4/5ths full.

Fill tub with water about 4/5ths full.

Attach air pump to side of tub.

Attach air pump to side of tub.

Thread air tubing into top of tank, plug it in, and make sure you have bubbles.

Thread air tubing into top of tank, plug it in, and make sure you have bubbles.

Don't Forget to Wash Your Hydroton Balls (9 Steps)

If you are going to use hydroton clay balls to offer support and moisture-wicking to your plants, you have to rinse them off quite well to avoid issues with the dust that they are covered in. I learned this the hard way.

About a week after getting this tub going, I began to see the roots covered in a rusty goop. It was the hydroton dust. I had to re-pot the tub. Luckily, I had over-planted my seeds and had plenty to replant right away.

Here's what I did:

  1. I filled the tub about a third of the way with water.
  2. I dumped the hydroton balls into the tub.
  3. Using a paddle, I stirred the balls vigorously for a few minutes, then let them soak for an hour or so. There was tons of chalky orangish dust in the water by this point. I removed the balls and put them into a gallon bucket with small holes in the bottom, then I drained and cleaned out the tub.
  4. I ran the hose over the gallon bucket, spraying intensely and agitating the balls. I then filled the tub again with fresh water and let them soak for a while. After an hour or so, I came back and repeated the process, spraying off with the hose, draining the tub, and letting them dry. It's a process, I'm telling you. And the dust never seems to be completely removed. But this will save you time in the long run, and a definite heartache seeing roots covered in dust.
  5. Next, you want to fill your tub with about 4/5 full of water. When your net pots rest in their holes, you want about the bottom 1/4 inch of the pot to be submerged. I use a level to make sure the tub is sitting so the water level inside will be the same for all the pots.
  6. Then attach the air stone to something heavy enough that it doesn't float around. I used a masonry brick that had broken in half and used a zip tie to bind them. You want the air stone to rest in the center as much as possible.
  7. Next, attach the air pump to the reservoir tub. A simple screw, as close to the top as you can get it, will work.
  8. Thread the air tubing through a hole in the top and connect to your air stone.
  9. Now plug in the pump and make sure it makes those sweet airy bubbles. My air pump has 2 airports. My line of thinking was economy. The cost of one air pump to provide aeration to 2 hydroponic tubs seemed like a good idea. I will monitor throughout to make sure it provides enough aeration. So far, it seems to be working well.
Add nutrients (flora micro 1st!!) to water reservoir.

Add nutrients (flora micro 1st!!) to water reservoir.

Adding Nutrients to the Water Reservoir (2 Steps)

I only have experience with general hydroponics nutrient solutions, although there are many different options on the market. For this project, I will only discuss the nutrient solution I use.

General hydroponics has a starter nutrient kit. The three main ingredients are FloraMicro, FloraBloom, and FloraGrow. Inside the kit was a general feeding schedule and how often to add the different nutrients.

  1. The initially recommended serving was 2.5 ml per gallon of each of these three solutions. I figure there are 17 gallons of water in my reservoir. I decided on about 45 milliliters of each.
  2. The instructions mention that the best results are achieved when you add the Flora micro first, so that is exactly what I did. I measured out each of the 3 solutions with a measuring cup and added them to the water reservoir.
Check pH levels until you hit 6.0(ish).

Check pH levels until you hit 6.0(ish).

Maintaining pH Levels (4 Steps)

An important thing to monitor throughout the plants' lifespan is the pH level of the water and nutrient solution in your reservoir. You will need either a test strip kit or a digital pH tester. I went with a digital tester as it is re-usable and easy to use.

  1. After your nutrient solution has been added, allow 30 minutes for the mix to disperse and stabilize, then take your tester and gauge the pH level. Most hydroponic experts agree that the proper range is between 5.5 and 6.5. The goal should be to keep it right at or around 6.0. Raising and lowering the pH level is a necessity due to the different variables and nutrients you will be adding throughout the course of the growing seasons.
  2. Don't spend a bunch of money on chemicals that raise and lower pH levels. There are two basic ingredients found in nearly every home that can accomplish this task with ease and economy:
    -Vinegar to lower the pH level.
    -Baking soda to raise the pH level.
  3. Add small amounts directly to the water until you are as close to 6.0 as possible.
  4. Monitor the pH level every other day. Consistency will lead to the best results.
Place your seedling into hydroton filled net pots.

Place your seedling into hydroton filled net pots.

Planting Your Seedlings Into the Net Pots (4 Steps)

Now it's time to "plant" your seedling. You want to see at least an inch of root descending from the bottom of the starter pod. This will help to ensure the seedling is strong enough.

  1. Drop enough of the hydroton into the bottom of the net pot to cover the bottom.
  2. Place your starter pod in the middle of the pot (roots down). Try to thread the roots straight down and out of the bottom of the net pot.
  3. Surround the pod with the hydroton to keep the pod balanced and straight up and down.
  4. Place pots in desired locations in your finished tub.
Place all filled net pots into your finished tub.

Place all filled net pots into your finished tub.

Further Reading

  • 3 Fast-Growing Hydroponic Plants
    If you've ever had a hydroponics system, you know how frustrating it can be to wait for the first harvest. Explore some fast-growing hydroponics plants to prevent that frustration.
  • 25 of the Best Plants for Indoor Hydroponic Gardens
    Do you worry at what might be sprayed on your lettuce and other vegetables? Why not grow it yourself using an easy hydroponic system? No dirt means no mess, just healthier and faster growing plants.
  • All You Need to Know About Hydroponics
    With everything happening around the world, it's no wonder we worry about our future. A hydroponics system is one way we can provide for ourselves without having to rely on others.

This content is accurate and true to the best of the author’s knowledge and is not meant to substitute for formal and individualized advice from a qualified professional.


Russ on April 18, 2020:

Many people are using water pumps but you are using an air pump? Why is this your recommendation?

Jeanie on April 24, 2019:

1) Does regular paint adhere to the tub? Or did u use a paint for vinyl/plastic? I have painted a plastic surface before and the paint began to peel within weeks.

2) Do you have a price list for the project start up?

Eric Brown on October 21, 2018:

Lemon juice also works great if your water is too alkaline and you want to lower your ph.

Louis Fourie from Johannesburg, South Africa on July 18, 2013:

Great hub.

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