Introduction: Hydroponic Float System

Picture of Hydroponic Float System

This is a completely passive hydroponic float system suitable for fast growing crops in cool weather

Step 1: Here's a List of What You'll Need

a container
a piece of 1.5 to 2" sheet styrofoam cut to fit your container
a 2.5" hole saw
foam cups
Jiffy peat pellets

Step 2: Drill Holes Through the Styrofoam

Picture of Drill Holes Through the Styrofoam

you'll probably have to drill through from both sides. I made a template for my hole spacing

Step 3: Now Prep Your Cups

Picture of Now Prep Your Cups

Tear a couple holes in each cup and them place them in the frame, they need to stick through no more than a quarter of an inch

Step 4: Mx Up Your Nutrient Mixture

Picture of Mx Up Your Nutrient Mixture

either use a good hydroponic nutrient OR two teaspoons of miracle gro + a teaspoon of epsom salt per a gallon OR two teaspoons of peter's 20-20-20 per gallon.

Step 5: Finally Put It Alltogether

Picture of Finally Put It Alltogether

pour the nutrient solution into your container, place the foam in the solution, place the cups in the holes in the foam and drop the long forgotten peat pellets in the cups, wait an hour or so for the pellets to swell up and sprinkle your seed on top of them and you're done.

Yield can be improved by the addition of an airstone and pump, but then you lose the convienience of a purley passive system.


trebuchet03 (author)2006-10-10

very nice... technically using peat removes the hydroponic name from it... but meh, who cares what "they" say? What will you be growing? That looks perfect for baby lettuce :D A -- this is one of my favorite growing methods. You can also used recycled plastic cups from a local college party... Just wash out those red beer cups :P

You weren't supposed to notice that! Still over the lifetime of the crop 6-8 weeks the leeching of nutrients from the peat should be minuscule since they're tied up in organic compounds that need to decay. Rockwool could be substituted. It is for lettuce, can't believe I forgot that. loose leaf not head lettuce

I still don't think that this is real hydroponics. I think it is sorta an hybrid system.

Rich1953 (author)zachninme2016-02-13

Search hydroponics and DWC

savvy9999 (author)2006-10-11

Nice job. That hole-cutting exercise is just screaming for a hot-wire setup. One question-- do you leave the big foam tray (with all of the little peat/seed cups) floating in the container 24x7 for as long as you're growing, or what?

Rich1953 (author)savvy99992016-02-13

Yes, do a search of "Deep Water Culture" or DWC hydroponics

trebuchet03 (author)savvy99992006-10-11

be sure to use an opaque container though... otherwise you're asking for algae problems (nutrient rich water doesn't help that either :P).

Yeah it's like ron popeil "Set it and forget it", once you put it together it just floats until harvest time.

AndrewL116 (author)2016-01-24

when designing a system its also good to keep in mind that some plants prefer nitrate and, while others prefer ammonium , mixing the two in the right balance allows for more efficient nitrogen removal from the system, there is information on which plants uptake which , corn uptakes both, is tricky to grow hydroponically but I found they keep nitrogen levels in check.

SaraiS2 (author)2016-01-10

I have a well established 30 gallon fish tank. After doing some aquaponic research, I decided to give it a try. Its a bit different that your suggestion, but same basic idea..

I took foam board, cut holes in it (various sizes, will explain). Then used a nylon stocking to cover the board on the bottom, so my plants dont fall through, and can hopefully still push their roots through. That's my theory, Ill let you know if it works. I didn't have netting pots available, but did have nylon, and foam. In my holes I have tiny seeds (lettuce and Kale),1 baby spider plant (I pushed the roots through the netting), and 2 fresh avacado seeds (large). I did a few diffent things to see how and if things would grow.

I wanted to know if I could start the seeds directly on the water. They are not submerged.They are sitting on top of the nylon, on top of the water.The bubbles coming from my air pump are misting them. I am hoping they will open up and give root, and that the root will push through the nylon to reach the water. If not, assuming they do start as is, I will gently pull the roots though when its time. The avacado seeds are sitting snug in the foam holes and are 1/2 way submerged, with the netting underneath. Again, hopefully the roots are able to push through the netting, but if not, when the time comes, I will push them through.

This is just a prototype. I did not have to go to the store and buy any materials. I am currently working on a different type of Aquaponics test, Also using materials I have at home. I have a Plant trough (small plastic planter box) and made a drain pipe in the center to control water level, that drains back into the fishtank (gravity drain. It is on top of the tank). A pond pump that draws water from the tank, and pours it into the plant trough. There is gravel in the trough, and the plants will sit in the gravel (havent gotten this far yet). I have also read that you can put seeds directly into the gravel, and I plan on doing it. So basicly, the plants are fed by the fish waste (poop, and uneaten fish food), the water is filtered by the gravel, and then drains back into the tank. Good for the fish, good for the plants! And a great way to recycle water.. as opposed to 90% of water being wasted by planting in the ground.

I will keep everyone updated. And make changes to my systems as I learn more. Again, these 2 projects cost me 0$ because I had all the materials needed already:

Pond pump, existing fish tank, foam board, nylon stockings, gravel, plant trough, small piece of pipe (for drain), seeds

stephenp5 (author)2015-03-14

Couldn't you use this to grow cannabis in a stream??

gijoes2000 (author)2008-01-17

I have an inground spa that I am not using as such and was wondering if I could apply a Hydroponics usage to it? I would like to grow some vegetables but really do not know if it will work by doing it in a spa - I do have a filtration system and blower but no heater. Any advice would be welcome!! Thank You!

Ceefa (author)gijoes20002008-11-14

Hi gijoes2000, If I had an inground spa that I wasn't using I'd be looking at aquaponics - keep fish in the spa and recycle the fish water through the hydroponics beds to provide the nutrients for the plant growth and at the same time clean and aerate the water for the fish. Google aquaponics and have a look at it. This instructable is awesome and my suggestion is not to steer you away from doing it but rather to open up the possibility to you of a greater use for your redundant spa. Ceefa

pellefson (author)Ceefa2011-10-05

I've been looking into Aquaponics also, and that's a great idea!!! You can get free spa's on craigs list all day long if you have the means to pick one up and move it.... hell, you could build a nice landscape of rocks and plants around the spa, fish in the spa, and beds of plants all around it... a perfect circle!!! i love it!!!!!!

VicinSea (author)gijoes20002008-07-15

I have seen this system used in a child's wading pool($6.00 at WalMart). I don't see any reason your spa wouldn't work except you will need to run it on low pressure with no filters. That would keep the fluid nicely aerated. I imagine that just running the pumps would be fairly cheap. In the winter you could run the heat too, at the lowest level. Tomatoes, especially would love that. Eggplants and peppers would also.
Wading Pools

Ahmos (author)2010-07-23

very nice

Geronima B Angeles (author)2009-06-14

I wonder why containers used in simple hydroponic system are always plastics and not transparent glass. Can I possible used transparent glass for me to view the growth of the roots?

Yep, roots don't like light, and also lots of nice, warm, and nutrients-filled tap water, if exposed to light, is the perfect algae growing medium.

From the reading I have done I have found that plant roots do not like the light and the plant will not be healthy if the roots are subjected to lots of light.

From what I understand most people use solid containers vs transparent ones because it hinders algae growth. The algae needs sunlight to grow and if you have a solid colored container it keeps the light out. You could use a transparent container if you had a way to cover it up when you aren't looking at the roots. If you used an old fish tank for example, just find some black paper and tape it up on all sides. Then pull the front sheet off when you want to look at it.

wilson.joe (author)2008-05-11

using miracle grow or peters 20-20-20.. you ever really look at the contents in miracle grow? a nice trace of arsenic for openers. besides miracle grow by itself wouldn't grow crap without the nutrients its missing that soil already has. I would prefer to use something like Iguana Juice from my local hydroponic store, its all organic and contains everything that is required for healthy plants without the toxins in miracle-grow that appear to be a something concocted by someone wanting to dispose of nuclear waste without building up a landfill, spread it around the world why not.. Im sorry If one is going to go all out green they need to remove miracle grow from their diet.. especially if one is what they eat.. .Great system by the way..

ja.dzado (author)wilson.joe2009-06-15

lol. arsenic is nuclear waste. lol.

Well, I looked iguana juice has slightly MORE arsenic than peter's and MORE than miracle gro

wilson.joe (author)2009-03-31

those peat pellets for perfect size of 2 inch net cups... and it might be a hybrid system but by the looks of things it works quiet well..

xfirexstarzx (author)2008-03-20

Out of curiosity, what is the epsom salt for? is it to prevent root rot? This is an awesome instructable! I tried this and the lettuce is about 8" tall already. I also planted tomatos, and cucumbers. The tomato plants are about 5" tall and the cucumber plants are about 4" tall. I grew mine indoors so far because it is snowing out right now. Thanks!

008 (author)xfirexstarzx2008-10-27

I'm curious as to how these plants will be able to keep themselves from toppling over when the tomatoes start growing. Would you have to build a cage around your container to tie the tomato plant to?

xfirexstarzx (author)0082008-10-29

I intended to put them seperately in pots after they got large enough, but they slowed down growing when they got to about a foot tall, so I eventually planted them outside. The cucumbers were also planted outside, then died of the blight that is going through my area. The lettuce turned out awesome and the tomatos took off after being planted outside. Thanks!

The epsom salt provides magnesium, after nitrogen, potassium and phosphorus it's the most important nutrient, and is involved with calcium transport, if I remember correctly. Thank you

Kaiven (author)2008-08-16

:D :D :D :D :D i just made one! its soo cool! ill post pics if it works! :D :D :D :D :D

IkilledKenny (author)2008-07-11

use liquid earth.

ths (author)2006-10-24

Hydroponic mean no dirt, only rock (aquarium rock) and water (well + nutriment)

jeffconnelly (author)ths2008-04-24

I agree with ths (and this)

Tool Using Animal (author)ths2006-10-25

Split whatever hairs you care too, if you go by the definition of hydroponics as promoted by the inventor (Gericke) then even the use of rocks precludes the use of the word hydroponics. And to muddy the waters even more peat is used to make "soilless potting soil"

feelgoodlost (author)2008-03-22

if anyone is interested heres a very basic course on growing plants in a greenhouse, its at least a great help with alot of general terminology

Red_Icculus (author)2007-08-13

The addition of an air pump would accelerate growth compared to a passive system.

capra_mcg (author)2007-06-13

I am very interested in hydroponics on a scale that would feed my family. Can think of many problems having to do with plants whose root systems are much smaller than then visible parts of plants. Weight imbalances for things like tomatoes or any plants that have large/heavy fruits. I have tried germinating in a soil-less environment with great results. I used two pieces of interfacing (sewing material that keeps collars stiff) and placed the seeds between the layers. Then I supported the layers on a piece of styro but allowed the edges to hang down below the styro. The styro is placed in a seed-starting tray with about a 1/2 of water. A dome lid is placed over it and the whole thing set in the sun. The interfacing wicks up the water as needed to keep the seeds moist, and the dome seals the moist/warm air needed for quick germination. Once the seeds have sprouted and have a true set of leaves, you can cut the interfacing and place the whole thing into soil or whatever medium you chose to grow in. It was fun and satified my need to 'know if it could be done'. You can find stuff to do similar germination on the net, BUT it is way expensive (10 germination pods for $8 + s/h). I got a piece of 45" x 36" interfacing for $1 at Wal-Mart. I love the savings and the results. FYI - searching net sites for 'Canabus' and 'hydroponic' will usually give you lots of interesting things to try. Great tips too. Saw a tip about rinsing plants prior to harvest to remove excess salts. They flushed the nutrient solution to just plain water a day or two (I think) prior to harvest. Sounds like what I need for my lettuce which seems to always have an overly salty taste (I use reclaimed water which has some chemical that burns certain plants). Maybe because I spray the lettuce from above (grown in soil right now), it absorbs too much of this chemical. Maybe using hydroponics would eliminate the problem if I water from the roots and then flush prior to harvest. Any comments would be welcome.

monkeyweather (author)capra_mcg2007-06-25

You might try using water from your fish tank if you have one. Save doing all that mizing of formulas. Let the roots go into the water. When you want to refresh the water, dump what's "used" into the garden, and clean your fish tank again. Plants love fish wastes, and they'll actually clean the water nicely enough that your fish can tolerate that same water again. Saw one example on the web of plants growing right OVER the fish tank to save a step.

aperkins01096 (author)2007-04-19

Thanks for the instructable! Trying it out myself with "Vitamin Greens" from Johnny's Select Seeds. Four days and now there's growth. One tip if anyone's cups are floating too low: take a second cup, cut off 1/4" from the bottom to make a "sleeve". Set the original cup into that, then drop it back in place. Propped mine up to the proper level (I was using a close approximation to a hole saw to cut my styro: an almost proper sized tin can, "opened" sideways to make a cutting edge). Pics on my site at

marcward86 (author)2007-03-03

so, do you set it outside in the sun, or near a window? and what sorts of plants can you grow?

outside. It's a good system for fast growing cool season crops, lettuce is perfect, mustard greens, and mesclun mix have worked as well.

chefmichel (author)2006-12-06

Very nice hybrid setup. What do you grow in London in the winter ?? I like your octaeder template. I use recycled modified yoghurt containers in my hydro setup.

I don't grow anything in London, I was making what I thought was a witty comment, the guy teased me that I misspelt "purely" so i just made a joke using the fact that I knew my misspelling was a suburb of London "Purley". Sorry about the confusion, actually i live in the southeastern United States, winter is our main growing season.

Nowbody is purfect

Tool Using Animal (author)2006-10-26

And just for the sake of an update i went out and changed from a quarter strength starter nutrient solution to a full strength, here's a pic

Junkernaut (author)2006-10-16

Simple and effecitive. Brilliant!

Speidumb (author)2006-10-12

Ah... a purley passive system... I like purls... :D

Actually it's a system designed strictly to be used in a particular suburb of london. BTW Trebuchet I use 7 gallon tubs that are sold at home improvement stores for mixing cement in, as the container.

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