How to Build a Styrofoam Hydroponic Floating System

Amongst the myriad of hydroponics systems out there, the floating raft system is one of the simplest to build and is an excellent option for those trying hydroponics for the first time. This styrofoam hydroponics system will also be useful to experienced growers as it can be scaled up for larger commercial farms. 

Floating raft systems are built from styrofoam containers filled with water and nutrients, with plants seated at the top, and an air pump to supply oxygen within the solution. Although this hydroponics system can’t be used for growing larger plants, it is still suitable for growing leafy vegetables like lettuce, spinach, kale, and much more. 

Things to look out for in a floating raft system

Although this is one of the easiest hydroponic systems to use, there are still several aspects that require the care and attention of growers. 

Maintaining an oxygen supply

To survive and grow healthily, plant roots need to have consistent access to oxygen, either from the surrounding air or from dissolved oxygen in the water supply. Roots can die if they have too little oxygen, cutting off the nutrient supply from the root region, and thereby allowing pathogens to grow and spread quickly. 

Grow mediums contain high quantities of atmospheric oxygen, and nutrient solutions can keep 6 to 13 ppm of oxygen at full saturation. However, warmer temperatures will mean that the water will hold less oxygen. As such, you must keep a high level of oxygen within the system using air pumps, air stones, or a water pump. 

Managing nutrient content and depth

Secondly, it is important to consistently check for any changes in temperature, EC (electrical conductivity), and pH level of the water and nutrient supply. This is because original levels in the water and nutrient solution will change as plants take in more water than nutrients. This also results in the accumulation of salts, hence it is important to do a partial or full replacement of the solution. 

Also, the surrounding climate can also affect the temperature, EC, and pH levels of the solution. If you live in a warmer region, it is advised to use a chiller to maintain the system’s optimal temperature. 

Thirdly, hydroponic containers should have sufficient depth ranging from 12 to 23 cm – allowing the solution to have better-buffering capacity and boost the productivity of plants. 

Preventing pathogen growth

Plant diseases and rotting are some of the dangers posed to hydroponic systems. Pathogens can quickly spread and infect all plants sharing the same system, even if it is well circulated. 

To prevent this from happening, be sure to maintain the optimal temperature, EC, and oxygen levels in the system so that the plant roots remain healthy. 

Building a styrofoam hydroponic raft system

Styrofoam hydroponic raft systems are suitable if you intend to grow plants in a small space, or if a set of plants require different EC or pH levels than others. 

The size of your container will depend on the size and number of plants you intend to harvest. Bigger plants like lettuce will occupy about 8 to 10 square inches of space, whereas smaller vegetables will allow you to grow more crops. 

Materials and tools:

  • Air pump
  • One 72-in. air pump tubing, black
  • Large-sized airstone
  • Container with a capacity of 53 liters, black
  • One sheet of polystyrene foam, measuring 2 ft by 2 ft by 1.5 in.
  • Nine net cups
  • Nine Rockwool rooting plugs
  • One compression grommet, measuring 1 by 1/4 in.
  • Nutrient solution 
  • One pack of growing medium – expanded clay pebbles  
  • A chuck drill
  • ⅜ in. or ½ in. chuck drill bits
  • One ⅞ in. hole saw bit 
  • ⅜ in. drill bit 
  • Coping saw, or any tool suitable for cutting foam
  • Knife for cutting through tubing 
  • Marker pen

For your hydroponics tank, try to purchase a rectangular shaped one, with smooth walls and minimal indents around its edges and sides. This will allow you to fit in your foam sheet more snugly.

Steps for building a hydroponic raft system

  1. Trace out the rim of the container onto the polystyrene foam, leaving a gap of a few millimeters around the entire edge. 
  2. Measure the length from the inner to the outer edge of the container. If the tank has any handles or dents along the inner wall, you may want to account for that as well.
  3. Ensure that the size of your polystyrene allows it to move down the tank for as much as four to eight in., since water levels will drop. 
  4. Mark out the places to insert your nine net cups or pots, making this an evenly spaced, three by three layout. Ensure the outer markings are marked with enough space away from the outer rim of the tank.
  5. Use the ⅞ in. hole saw to cut out holes in the foam sheet.
  6. Place the foam sheet inside your tank and mark out the point it has dropped to within the container. This will indicate when it is time to top up your nutrient solution when it drops. 
  7. Taking the ⅜ in. drill bit, drill a hole in the side of the tank and insert the compression grommet. Thread the air tubing through the hole, with one end joined to the air pump, and the other to the air stone.
  8. Place your seeds in the Rockwool plugs and allow them to germinate till their roots extend from the bottom. Once germinated, place them inside the net pots and refill it with the clay pebbles for support. 
  9. Fill the tank with water and nutrients, and measure the pH levels. Replant the germinated seedlings and place the system in sunlight or under grow lights. 
  10. Once the solution in the tank has fallen by two to four in., fill it up again. Remember to top up the solution now and then with water or nutrient solution that is ¼ times the original strength. 

If you worry about a nutrient burn, it is safer to start with a weak strength nutrient solution and bump up the strength as your plants mature. 

Final tips

When deciding on the type of plants, opt for lighter crops so that the polystyrene foam can support them throughout their growth stages. Additionally, select plants that grow well in wet conditions, like lettuce, bok choy, and collard greens. 

In marking out the positions of where to place your netting pots, always take into account the matured sizes of your crops. Space out their positions accordingly, and with enough room between them avoid overcrowding. 

Cheap and simple to construct, the hydroponic floating system doesn’t require as many materials and tools as other grow systems. Don’t forget that the internet is your best friend if you ever need tips and advice on issues like pest control and maintaining pH levels. Be willing to monitor the growth conditions throughout all growth stages, and you are well on your way to harvesting a healthy crop of plants. 


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