Plant walls, gardening and the science of aquaponics

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I have a lot of posts on my blog about plant wall and growing plants in felt.  I thought it might be beneficial to give an overview of the science behind plant walls fed by fish.

I’m not dealing with PH in this page, I’m just dealing with the nutrients needed and supplied. (If you don’t want to slog through this whole article scroll to the cliff notes version at the bottom. Be warned, you’re gonna miss a lot if you do.)

Plant walls are all about the science.  It’s all about what the plants like, what the plants need, how the world works.

Before I get too far into this, please understand I backed into building plant walls.  My first project wasn’t the plant wall pictured here.  I started with an outside fish tank with good sized carp (goldfish and shubunkins).  My sister-in-law Vala, bless her heart, got us started toward having healthy fish.  She looked at the fish and said “your fish are sick.”  ACK!  We did lots of water changes (a challenge with a low draw well), fought parasites, fungus and fin rot and suffered through fish dying due to our ignorance.

Thus began the journey toward lazy summers with no water changes.  That, of course, led to growbeds, plant walls , indoor aquariums and a new addiction, but I digress.

Here’s the basic of what you need to know.  Fish need clean water.  Plants need food.  Fish can supply the food and plants can clean the water.  That’s the situation in the simplest of terms.

There are two ways you can keep the water suitable for raising healthy fish.  One way is to dump a percent of the water weekly and add fresh to dilute the pollution load.  I have two problems with this method of water quality management.  It’s wasteful (and a real PITA if you live in town and have chlorinated water) and it’s time consuming.  Remember me, Ms. Lazy?  Repetitious work is SO not my thing.  Every time I dumped water out of Wadly’s big tank I invariably got my feet wet.  Yuck.  Add inconvenient and messy to the list of issues I have with water exchanges.  If you’re paying for your water, add waste of bucks to our expanding list of annoyances.

But there’s another way.  You can marry fish and plants and have clean water, healthy fish and pretty plants that grow and bloom and clean the air.  Ah . . . . a veritable Hallmark moment!

Did you know plants use nitrates as food?  They do!  And with a little biological magic and a little patience, the polluted water can supply plants with the nitrates they need to grow and be beautiful.  No water changes, no treating the water, no fertilizing and watering the plants twice a week . . . no kidding.

Here’s how the science bit of it works.  When fish breathe (yeah, who woulda thunkit) and poop, ammonia is released into the water.  Nitrifying bacteria eat the ammonia and poop out nitrites.  Notice I said nitrITes, not nitrATes.  Plants use nitrates, so with the conversion of ammonia to nitrites we’re only halfway to our goal.  Then other nitrifying bacteria eat the nitrITes and poop out nitrATes which is what we need for our plants. Isn’t that awesome!?  Mother Nature at her best!

To clean the water we need to feed those lovely nitrates to our plants.  Here’s where we run into the next problem.  We have to get the water cleaned without losing it.  We want the water minus the poopy bits.  We could just dump the water on plants in the yard, but hark back to my note on mess and effort.  SO not me.  We need a way to get the nitrates out of the water while still using the water for our fish.

And this is where aquaponics, hydroponics and plant walls come into play.  They are beautifully effective at removing the pollutants from the water.

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A plant wall is just a big biofilter.  So is a growbed.  So is the tub of plants that cleans the polluted water of the big outside tank.  The water cycles through that tub of water plants and the roots of the plants filter out all the fish poop particles and nitrates before the water returns to the main fish tank.  The fish stay healthy and the water is clear all the way to the rocks and potted water lily on the bottom.  I have a summer of beautiful water plants and healthy fish and NO water changes.  Bliss.  This is where I got started, keeping Wadly’s tank clean and his fish healthy.  I didn’t do it for Wadly, I did it for me; so I could do less and have more.

Here’s how the plant wall came about.

I fill waiting time doing research on things that interest me.  You know the motto, “never stop learning.”  That’s me.  I was learning about building vegetable growbeds for the outside fish tanks (we have more than one) when I ran across a vertical garden done by Patrick Blanc.  The whole concept was so awesome I HAD to try it.  Have you figured out I like experimenting and solving puzzles?  I collected bits and pieces, extrapolated information from what I read and I put together a plant wall.

Plant wall on April 16, 2009.  Is my neophyte plant wall pathetic looking enough for you?  <grin>  It got better.  And it got better fast!
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Because of the research I’d already done on growbeds I knew my test plant wall would run really well using water from one of the fish tanks.  In that tank the nitrifying bacteria had already cycled (completed the cycle of ammonia to nitrates) and all I had to do was dip fresh tank water out of the tank once a week.  Cool!

After the third or forth water change I was getting pretty tired of the mess and effort.   I thought, what if I chucked some fish in that bucket!?  Then I wouldn’t have to move my big house plants to refill the bucket every week, I wouldn’t have to haul water, I wouldn’t have to deal with the mess of pulling the pump out of the bucket to dump old water before adding the new.  All I’d have to do is chuck some food in the bucket every morning.  I could handle that!  That’s way easier than hauling water once a week!  So that’s what I did.

Blooming begonias
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I chucked five little goldies in the bucket and the plant wall grew and grew and grew.  It bloomed and grew some more.  And bloomed some more.

I top up the water in the bucket once a week.  Once I added too much and one of the goldies jumped out, wiggled under one of my planters and expired.  Oops.  Bring on a lid.  Then somebody gave me an aquarium with stand that was the perfect size to fit under the plant wall which only needed topped up once a month.  Then I had to have a pleco and a heater, then two goldfish died for no apparent reason.  The plants grew and grew.  The plants bloomed.  Bliss.

That pretty much brings us to this point.   I add a bit of potash when I top the aquarium up each month because that’s the one supplement fish poop doesn’t provide.  Life is good.

But now I want a bigger plant wall and I want to autofill the aquarium so I don’t have the mess of dealing with buckets of warm water once a month.  You know me. <smile> I want it all with the minimum amount of physical effort expended.  Work smarter, not harder, that’s me.  <grin>

Here’s the cliff notes version. If you want a plant wall to run on an aquarium of fish and you don’t want to replace the fish a couple times waiting for the nitrifying bacteria to grow and your aquarium to cycle, heed my words.  You need to have the nitrifying bacteria doing their thing all the way through to producing nitrates from ammonia to nitrates before you add any fish.  Read up on nitrifying bacteria until you understand and can predict the cycle.  This isn’t information I can spoon feed you.  Some gray cell activity WILL be required.  Buy yourself a master test kit and keep testing the water until the cycling is complete.  Make sure the PH is stabilized before you add the fish and the fish will live and thrive.  Your plant wall will thrive!  As your wall grows it will use more nutrients.  Test the water monthly to see if you need more fish or need to feed your fish more food.  Enjoy!

3 thoughts on “Plant walls, gardening and the science of aquaponics

  1. Hello! I’m currently co-authoring a book titled “Garden Up! Smart Vertical Gardening for Large and Small Spaces”, and one of the chapters is devoted to large scale, medium scale and DIY living walls. I love what you’ve done with your living wall and was wondering if you’d be interested in letting us a photo, giving you photo credit of course. If so, please send me an email and we’ll talk more about it. If not, thanks anyway and good luck with your beautiful wall! – Rebecca

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