Hydroponic Tanks: Everything you Need to Know

Consider your hydroponics tank the heart of your system. Your water reservoir, or tank, is what holds the very thing your plants need to live: the nutrient saturated water solution. Once you start looking into hydroponic tanks more, you’ll quickly realize that they’re more complicated than simply being a tub where you hold your nutrient solution. And that can get overwhelming. Don’t worry though, this guide has everything you need to know about hydroponics tanks:

The Function of Hydroponics Tanks

Hydroponics tanks are more or less the same in design and function, in essence. Naturally they hold the water and nutrients that will be delivered to your plants. How they do that is slightly different depending on the type of hydroponic system. Here’s a brief look at how hydroponics tanks function in different systems:

Ebb and Flow

Ebb and Flow systems are also called Flood and Drain systems. The tank doesn’t have to be located directly under or next to the growing tray, but it’s the easiest and most common setup. Using a water pump, tubing runs from the hydroponics tank to the plant tray, and floods the tray with water from the tank. The water reaches a certain level, and then gradually drains away. Many systems have a drainage line that returns unused water back to the tank.

NFT

Nutrient Film Technique systems work by moving water from the nutrient reservoir to plant tray in a constant stream. Roots sit in channels that the water then moves through (with the help of the growing tray at a slightly slanted angle). In this case, a pump is needed to move water up to the growing tray, although the tank can be located away from the plants as long as tubing permits.

DWC

In a Deep Water Culture (DWC) hydroponic system, the plants are suspended in a growing tray directly above the hydroponics tank. The roots hang into the water reservoir itself. Because of this, the tank has to be placed under the grow tray. Tanks in these kinds of systems need to have an air stone to provide extra aeration that they lack otherwise.

Drip

With a Drip system, it’s also more common to place the hydroponics tray directly underneath the growing tray. This also helps to conserve any runoff water. Drip systems get water to plants through tubing that brings water from the reservoir to the growing tray. From there, each plant gets water through holes placed in the tubing.

Wick

In a Wick type system, the hydroponics tank has to be placed directly under the growing tray. That’s because the tray has holes in it that allow an absorbent cord to connect from the tank into the tray’s growing medium. Basically the cord soaks up nutrient solution from the tank, the nutrient solution travels up the cord, and is then absorbed by the growing medium and roots.

Finding the Right Tank for Your System

The biggest part of putting the right tank in your hydroponics system is making sure it’s a good fit. While any old tub can surely hold water and function as your tank, if it isn’t sized correctly you end up with either not enough water for your plants, or a pointless excess. That being said, it’s far better to end up with a pointless excess. The capacity of your tank is going to mostly rely on your plants, but most hydroponic gardeners prefer to double the amount of water their plants need when sizing their tank.

Here’s how to make sure your tank is the right size:

First, take note of how many plants you have (or plan on having). Then also make a note of how many plants are small, medium, or large. If you’re unsure, it’s better to estimate up and account for the mature plant’s size.

Here’s a rule of thumb you can follow to determine how much water your plants need:

Large plants – require a minimum of 2.5 gallons per plant

Medium plants – need between 1 and 1.5 gallons per plant

Small plants – should get at least .5 gallons per plants

Look at your list of plants, and use the above list to determine how much water your tank needs to hold. Basically, just add up the gallons you need for each plant, and you’ve got your answer.

As an example:

Total plants: 12

Large plants: 2                                           Water needed: 5 gallons

Medium plants: 6                                       Water needed: 9 gallons

Small plants: 4                                           Water needed: 2 gallons

Total water needed: 16 gallons (minimum)

As you can see, it’s not difficult to see how much your tank needs to hold. In this case, the tank would need to hold at least 16 gallons, but a tank that could hold a few extra gallons would be better (and give you a good, safe margin). Keep in mind, that number is very much a bare minimum. Doubling the minimum water needed gives you 32 gallons, and a better chance of thriving plants.

So, You Want to Make Your Own Hydroponics Tank?

Making your own hydroponics tank is easy, and it saves on money. For that reason a lot of people choose to make their own DIY hydroponics tank. You can recycle tons of things into a new hydroponics tank, as long as it’s an appropriate size and water tight.

Here are some ideas:

  • Old fish tanks
  • Plastic storage bins (just make sure they’re deep enough)
  • Large display boxes (plastic or glass)
  • Plastic trash cans (thoroughly cleaned)

Tip: Before you decide to use anything as your hydroponics tank, you need to be 100% sure it’s water tight. Fill the ‘tank’ full of water, and inspect it thoroughly for any leaks. If you don’t see any, it’s a good sign but you still need to let it sit overnight to be sure. If you want to be really sure there isn’t any leak, put a thin material like toilet paper or tissue paper around the floor where your tank is sitting. Even if water from a leak evaporates, the paper will show there was a leak by sticking to the ground.

Once you’re totally sure your tank isn’t going to leak, you need to clean it. Even if you purchased a container to use as your tank, you still need to clean it. You can use disinfectants to be sure it’s sterile, but you can also use a 50/50 mix of water and vinegar.

Now that your tank is cleaned up, make sure to give it a water rinse and dry it (especially if you used chemicals or disinfectants).

Note: you’ll also need to get some other gear to go with your tank, such as a pump, air stone, inline tubing, etc.

Extra Components You May Need for Your Tank

Your hydroponics tank itself is one of the most important parts of your hydroponic system. Alas, one soldier can’t win a war, and likewise your tank is going to need some help to work properly. Some things are totally necessary to add, while others depend on preference or the type of system.

Nutrient Solution

Nutrient Solution has to be added to your tank so that your plants get sufficient nutrients. With proper testing and regular maintenance, it should be easy to get on a steady schedule for adding nutrients and managing EC levels.

Tubing

Tubing is a pretty simple component of your tank, but it is going to be responsible for connecting your pumps, airstones, water, and plants together. Always make sure the tubing you use is free of damage, and food safe.

A Pump

Pumps have an important part in hydroponic systems. They move water from your hydroponics tank into the plant tray, via tubing that connects from the pump, through the reservoir (or tank), and up to the plants. Pumps are either inline or submersible. That means that they’re either located outside of your tank (in inline models), or inside the water of your tank itself (in submersible models).

An Airstone

Airstones add extra oxygen to the water in your tank. Basically, they connect to a pump with tubing, and air is pushed through the tubing into the airstone itself. This produces tiny bubbles that aerate the water. Airstones aren’t required for every type of system, but they do improve the quality of the water in your tank whether required or not.

Hydroponics Tanks: Location is Everything

Well, to be fair location isn’t everything. But it can make a big difference to your tank. In some systems, like DWC, tank placement is non-negotiable. Your reservoir has to be placed directly under the plants. In others, like Ebb and Flow systems, your tank doesn’t necessarily have to be placed anywhere specific, so you’ve got some choice.

Here’s where a lot of people mess up:

In the attempt to create a convenient set up, they place their reservoir close to their plants. Usually, as close as possible. While it’s a good idea, it actually causes more issues than it solves.

The first problem becomes evident pretty quickly, and it’s algae. Placed so close to the heat and lights around the plants, algae flourishes. Not only that, your tank becomes a breeding ground for fungi, bacteria, and microbes that can wreak havoc on your plants.

And let’s not forget that your water’s going to evaporate more quickly, leading to higher EC concentrations and more frequent water changes.

Not only can you end up with all kinds of contaminants, your EC levels can become so concentrated that your plants end up with burned roots. With a high temperature, plants have less access to oxygen (as the available oxygen in the tank is seriously decreased) and can ‘drown.’

Another side effect is that high temperatures can create a snowball effect. Since plants have to perspire to release heat from the water, they have to drink more water as a result, and therefore lower water levels in the reservoir and increase the nutrient saturation even faster.

Some hydroponic growers go to great lengths to avoid these issues; even going as far as placing their tank in another (adjacent) room, or underground. You don’t have to go that far, but don’t put your tank too close to your plants if you don’t have to. 

Let’s Talk a Little More About Your Tank Temperature

Hydroponic tanks shouldn’t have unregulated, unmonitored temperatures. Really, after you’ve got your system all set up you shouldn’t have to do much with the temperature of your water. That is, as long as you’ve set it up properly and found a way to keep a stable temperature.

The ideal temperature range to aim for is around 63 to 72 degrees. This range suits most plants and prevents conditions that invite bacteria and disease like root rot. What might surprise you is that you’re going to spend more effort keeping your tank water cool enough, rather than warm enough.

If you can’t find a perfect, temperature stable spot in your growing area, don’t worry. It’s a very, very common issue so there are plenty of solutions. Here’s what you can do:

  • Move your tank into another area, or insulate it by placing it underground (too much effort? Most people are in the same boat, so read on).
  • Wrap or cover your reservoir in a shiny, reflective covering, or a light colored coating. This will deflect some heat from seeping into your reservoir.
  • You can also use insulated padding around your reservoir in conjunction with coverings that deflect heat.
  • The last solution is more expensive, so typically commercial growers or very invested hobbyists are more likely to choose this option: purchasing a water chiller.

Why Is Maintaining Your Hydroponics Tank Important?

Briefly, let’s talk about why tank maintenance is so important. Setting your tank up correctly is going to give you a good start, but it does little good if you neglect your tank. Tank maintenance includes everything from testing your water and adjusting water levels when needed, to changing out the water, to cleaning out your tank and equipment, to keeping a maintenance log.

Without due care, the water in your tank can become a harmful, toxic substance to your plants. When water undergoes drastic changes in quality, pH, or nutrient concentration, it can put your plants into shock, burn roots, or invite disease and bacteria. Properly maintaining your hydroponics tank prevents the dramatic changes in the water/nutrient chemistry, as you’ll be able to correct problems before they spiral out of control.

Regular cleaning and water changes should be on a schedule to allow helpful organisms to remain, while harmful organisms are regulated and controlled. Even allowing too much algae to accumulate can take away from your water’s oxygen levels and create an ideal environment for microbes and fungal disease.

Tank Maintenance Guide:

Once you’ve got your tank selected, you’re going to have to do more than dump water in and call it good. Proper tank maintenance can protect your plants from a ton of problems, and once you’ve got a maintenance routine down it really isn’t that hard. Here’s a rundown of everything you need to know to keep your tank in great shape.

Test your water

One of the first things you need to do is begin a testing routine for the water and nutrients in your tank. Test your water regularly, and once your system is established aim to test at least once daily, although twice is optimal (Tip: test at the same time daily for better results).  When you test your water, you need to be looking at two main things:

PH: pH, or potential hydrogen, should usually be in the range of 5.5 to 6.5

EC: EC, aka electric conductivity, measures nutrient levels in your water and should be 1.2 to 2.0.

There are different testing methods you can use, but the easiest by far is using a monitor. Some monitors are even available as an EC/pH testing combo. Other testing methods include strips that are dipped into the water and liquid testing kits (a sample of the reservoir water is taken and drops of the testing solution change color to indicate levels).

What if my pH or EC levels are off?

For pH, there are a ton of readily available, commercial solutions to either raise or lower your pH. If you use one of these, make sure you follow the directions exactly, and test your water during and after changing the pH levels. If your EC is too high, simply dilute the solution in your tank with clean water. Test frequently, and add water gradually until you reach the proper level. If your EC is too low, you need to add more nutrients to your tank.

Taking care of the water in your tank

Besides just testing, you need to make sure you’re giving the water in your tank proper maintenance (which will also help reduce EC and pH level issues). There are two main things you need to do to keep you water in top shape in between testing: water top offs, and water changes.

Topping off the water in your hydroponics tank

Your hydroponics tank is going to lose water gradually, so you need to compensate for that. It’s best to start a routine for this right away, and keep to it. Another thing you should be doing is keeping a log of water top offs, which you’ll need later on.

Water top offs are easy, simply add water when you notice that your water level is lower. When you do this, make a note in your log of how much water was added. That’s pretty much it, just be prepared to top off your water every day or two.

Doing a water change

Every once in awhile you need to do a larger water change to help keep your tank problem free. You’ll do this every couple weeks, or every few weeks if your water doesn’t evaporate very quickly. Basically, you need to keep an eye on your top off log to know exactly when to do this. Once the volume of water you’ve topped off with is half of your tank’s capacity (added up over time), it’s time.

Simply remove half the water in your hydroponics tank and replace with fresh water. As always, make a note of the change in your log and test your water for pH and EC levels.

Cleaning out your hydroponics tank

Your hydroponics tank can gather up a bunch of nasty gunk over time, and while there are helpful things in there (like beneficial bacteria), you have to clean it. It can be tempting to shirk this chore, but your plants will suffer for it in the long run.

First, how do you know when it’s time to clean your tank? Well, you need to go back to your logs. Again, if you’ve been keeping good records, this step isn’t so hard. Monitor your top off log and when the volume of water from top offs totals the volume of your tank, it’s time to clean. Here’s another way to look at it, if your top offs equal half your tank’s volume in 2 weeks, you’ll be cleaning your tank about every month.

Here’s a quick example (so you know when to clean your tank):

Let’s start by assuming that your tank is 10 gallons (remember, we’re keeping it simple here). Now, here’s an example of what your log for top offs and water changes would look like:

Note: As shown in the chart, the larger water change is done when top offs equal 50% of the volume (1/15/19), and a cleaning would be done on the date after the last logged top off (1/25/19).

What can you use to clean your tank?

There are commercially available solutions that you can purchase to clean your tank with. Generally, these solutions should be food safe, plant safe, and contain minimal chemical content. But you don’t really need to go buy a special cleaner. You can use vinegar, bleach, or hydrogen peroxide, and they do the job just fine. Here’s the thing:

If you use bleach, take care. Your plants can’t come into contact with it, so only use it when you’re not growing anything. Hydrogen peroxide and vinegar are both safe around plants in small amounts (although still make every attempt to maintain as much distance as possible).

Start cleaning with clean tools

Don’t go to clean your hydroponics tank with tools that aren’t clean. The reason behind this should be obvious, and it’s a small, easy thing to clean your tools before you start. Even things like scrubbers (if you’re using them) need to be cleaned thoroughly.

Drain your tank

Disconnect any ancillary equipment from your tank, from airstones to pumps to tubing. Then, drain your tank. It shouldn’t have to be said, but make sure you’re doing this well away from any electrical sources.

Clean it up

After that you can do a preliminary spray down (if your reservoir’s gotten pretty gunked up you may want to use a pressure washer). Then use your cleaning agent to sanitize your tank started at the top and working methodically downwards. To make sure you’re killing all the germs, bacteria, and microbes, you can let the solution sit for a few minutes. Then, rinse your tank thoroughly to get rid of any solution that may remain.

Let it dry

Look, letting things air dry can be pain and it does make a chore take longer. That being said, if you can let your tank air dry it’s actually better. You can manually dry it out, but you risk leaving behind fibers or microbes. Running a fan can help expedite the process if you’re not the patient type. 

Note: you will also need to clean out the other parts connecting to your tank, such as tubing and filters. You can use the same process and solutions as you did to clean your tank.

Hydroponics Tanks FAQ

My water levels are out of control! Should I do a full water change?

Resorting to a full water change off schedule is, ideally, something to avoid. That being said, you need to weigh the severity of the situation vs the benefits of a full water change. Keep in mind that the pH of the water alone should never change more than .5 at one time. More than that can shock your plants. So it’s better to do more frequent, small water changes (while testing at each change) until you reach a safe level.

Does my tank need to have a lid?

Technically, no it doesn’t have to have a lid. But let’s be honest, it’s a really, really good idea to have one. First, you’re going to lose a lot less water from evaporation. That means your EC and pH levels are going to be more stable. Next, you don’t want debris dropping into your reservoir and mucking up your water; a lid makes this a non issue. Also consider that with a lid, it’s going to make regulating your water temperature much easier, which is better for your plants and your water quality.

Which is better for testing, a strip kit, liquid kit, or a meter?

The strip and liquid kits are accurate, although they do have to be replaced. It can also be confusing if the colors that show results are unclear. A meter (especially a combo meter) is more of an initial investment, but you’ll never question your results, nor have to buy another after x number of uses.

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About the Author

Oscar Stephens
Oscar Stephens
I am a gardening and tech enthusiast! Stumbling across the world of Hydroponics, Aquaponics and Aeroponics by accident I've decided to create TheHydroponicsPlanet to put all of the best information I can find in one easy to navigate place. I'll continue to add more content as I discover new things!