What Net Cup Size Should You Use in Hydroponics?

The net cup size does matter in hydroponics. If you choose a smaller one compared to what your plant needs, this might not support healthy growth and further lead to death. On the other hand, a bigger net cup may result in nutrients not being efficiently delivered to your plant roots!

Choosing a hydroponic net cup size depends on the plant type and hydroponic system. Growing leafy vegetables and herbs in a nutrient film technique (NFT) system may require 2” to 3” diameter net pots, while vegetables such as tomato and eggplant in a water culture system need 4” to 6” net cup sizes.

Aside from these factors, we also need to consider the food safety of net cups. What are the materials used in these net cups? Are they safe for hydroponic production? And more importantly, can we recycle household materials as hydroponic net cups? All of these will be answered moving forward.

Factors to Consider in Choosing a Net Cup Size

The hydroponic system and plant type dictate what net cup size is optimum for a hydroponic garden. For instance, peppers need bigger net pots due to their tall stature; while lettuce can grow healthily in smaller net pots because of its rosette plant form.

What are Net Cups?

Net cups, in hydroponics, are just like pots in a container soil garden. They hold and support the plant along with the growing medium. They have slits below to allow root growth towards the hydroponic nutrient solution.

Available Net Cup Sizes

Net cups are commercially-available in 2”, 3”, 4”, 5”, and 6” diameter.

The differences in sizes account for the different hydroponic systems available. Most of the time, net cups are already packaged with the hydroponic system. For example, if you purchase a Deep Water Culture system, it will naturally come with a 4-6” net cup.

However, knowing your net cup sizes will be handy for those who want to save money by making a hydroponic garden from recycled and/or household materials. If that’s you, you will absolutely be equipped with ideas when you finish this article!

Plant and Hydroponic System Compatibility of Net Cup Sizes

In general, the bigger the hydroponic system and plant size, the bigger the net cup size that goes from 2” for nutrient film technique to 6” for kratky and water culture.

To help you decide on what net cup size to purchase, we have matched hydroponic systems and plants with the best net cup options and summarized that for you below!

Hydroponic System	Plant	Best Net Cup Size (diameter in inches)
Nutrient Film Technique (NFT)	Lettuce Kale Bok Choy Strawberry	2
Kratky Hydroponics; Deep Water Culture(DWC)	Lettuce Kale Bok Choy Basil Jade	3-4
Kratky Hydroponics; Deep Water Culture(DWC); Dutch Bucket System	Tomatoes Pepper Eggplant Okra	4-6

Food Safety of Your Net Cups

Plastics #2 (high-density polyethylene) and #5 (polypropylene) are the safest options for a hydroponic net cup material.

Also known as resin ID, the abovementioned numbers represent the material used to make plastic products and can be found on the commodity enclosed by three arrows. Why is this important? Remember, not all plastic is safe for hydroponic food production!

Plastic #2 is commonly found in bottles and jugs; while plastic #5 is used for yogurt containers.

On the other hand, plastic #1, #3, and #7 are not ideal for hydroponics.

Plastic #1, polyethylene terephthalate (PET) is found in drinking bottles. This is not safe because it releases a harmful element i.e. antimony when exposed to hot temperatures.

Plastic #3, polyvinyl chloride (PVC), is commonly found in pipes. PVC itself was found to possibly contain toxins that can cause cancer and serious damage. With this concern, food-safe PVC such as unplasticized PVCs are already available in the market.

Plastic #7, which are the other miscellaneous plastics, is dangerous since they contain BPA which is toxic to the body as it affects the endocrine system.

This information is so useful for those who want to recycle net cups for hydroponics. So remember, before making a net cup out of household material, you need to check the resin ID first!

Commercially-Available Net Cup Alternative

One of the most promising alternatives for net cups is GrowGrip. It is a cheap and reusable option made from food-grade polyethylene foam material.

From the name itself, it grips your plant to support its stature. Because it only weighs less than a gram, this alternative is ideal for leafy greens such as lettuce, kale, and bok choy. This will also fit NFT and DWC hydroponic systems.

GrowGrips are also chemically non-reactive, which means they do not have an effect on pH, unlike other alternatives like peat plugs.

Furthermore, after every growing season, GrowGrips can be reused after bleach sterilization.

DIY Hydroponic Net Cups

Choosing a food-grade and safe material such as Plastic #2 and #5 must be the first consideration. Household materials such as disposable cups or styrofoam cups are the most common items being transformed into hydroponic net cups.

Just a friendly reminder: Make sure that your chosen net cup alternative will fit into the hole in your hydroponic system. So before doing the steps enumerated below, measure the holes in your hydroponic system first; then measure your cup if it will fit well.

Option #1: Styro Cups

1. Turn your styro cups upside down.
2. Using a cutter, cut 3 to 5 slits below the cup.
3. Remove the cut parts and clean the net cup.

Option #2: Disposable Plastic Cups

1. Make sure that the cups have 2 or 5 resin IDs. This could be yogurt containers, plastic bottles, and even party cups!
2. Let the soldering iron become hot.
3. Using the soldering iron, poke 10-20 holes at the bottom part of the cups.
4. Let the poked parts dry.

How to make your own Hpdroponics or Aquaponics Net Pots and save money

I know that as you read through this, there are questions running through your mind.

1. Is it More Practical to DIY?

Let us face it: it is so much cheaper. On average, net cup prices on Amazon range from $5 to $10 just for 12 pieces. For styro and disposable cups, you can have 50 pieces of them just for $18! (Even cheaper than that for those packed in 100s).

So if you are still a hydroponic gardening beginner, I recommend starting with DIY net cups, and then gradually switching to commercially-available net cups.

2. Isn’t it Time Consuming?

I have tried making net cups from styro cups last year. In my experience, I can say that finishing 1 net cup will not take you longer than 1.5 minutes. The same through goes for poking holes in disposable cups using a soldering iron.

However, a risk in using a soldering iron is damaging disposable cups when the iron is too hot. This will also take a practice of control and patience!

3. So, What are the Pros of Purchasing Net Cups Instead?

They can last longer than those DIY. Thus, if you are planning to really focus on hydroponic gardening either as a hobby or to start a small business and further commercialize, investing in market-available net cups will be a wise decision.

Sources

• “A Suspended Net-Pot, Non-Circulating Hydroponic Method for Commercial Production of Leafy, Romaine, and Semi-Head Lettuce” by Kratky, B.A. in University of Hawaii at Manoa
• “Is Polypropylene a Safe Plastic to Use in Your Home?” by Stanborough, R.J. on Healthline