# Hydroponics works...so, why not use "regular" plants?



## Kreutz (Dec 24, 2010)

I was thinking since crops/plants can be grown in a purely liquid medium, must I limit myself to buying the common marine plants? Not saying I plan on growing lettuce in my tanks...but, in theory, couldn't I use a terrestrial plant that is flood tolerant like ferns and stick them in there? Tired of the plants available at the fish store!

Just "testing the waters" on this. Love to hear input/criticisms!


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## susankat (Nov 15, 2008)

The only way they would survive long term is to keep the leaves out of the water. I have seen people put the roots of some in their hob filters to help with filtration.


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## kellenw (Mar 28, 2010)

Sure. It's called aquaponics, and it's becoming more and more popular as a means of producing food in small spaces. Google AquaponicsHQ, AquaponicsCommunity, Practical Aquaponics or BackyardAquaponics.

I run several AP systems. It's a lot of fun and quite productive.


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## beaslbob (May 29, 2009)

Yes you can use plants like peace lilies roots in water rest in air. But IMHO one of the key important aspects of true submerged aquatic plants is that they consume carbon dioxide and produce oxygen. Which does not happen with the plants in the air instead of water.

my .02


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## snail (Aug 6, 2010)

You could always have a paludarium.


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## M1ster Stanl3y (Dec 10, 2010)

*cough* weed *cough* i mean hemp i heard works well. lol


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## Gizmo (Dec 6, 2010)

For normal plants to grow in a purely liquid medium, they have to have some very specific nutrients and fertilizers in the water which might not be condusive to aquatic life. I mean, would you want to be swimming around in MiracleGro liquid plant food?


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## kellenw (Mar 28, 2010)

[email protected] said:


> For normal plants to grow in a purely liquid medium, they have to have some very specific nutrients and fertilizers in the water which might not be condusive to aquatic life. I mean, would you want to be swimming around in MiracleGro liquid plant food?


I think you'd be surprised at how well aquaponics functions. Also, most, though not all, aquaponics systems use a grow media (gravel, kiln fired clay pebbles like hydroton, etc.). In a media based AP system, the fish tank water is run through the media filled grow beds where the plants take up the nutrients (nitrates and other trace elements). The fish waste and excess/uneaten food alone is capable of supporting non-aquatic plants quite well assuming you have a properly cycled system. Sometimes you encounter an iron, potassium or calcium deficiency, but these can be added to the system without any harm whatsoever to the fish. I have grown virtually every common "garden" vegetable in my aquaponics systems, and most of them tend to grow faster in my aquaponics systems than they do in the soil based garden.

The "cool" thing about employing aquaponics is that you basically never have to do a water change, because harvesting the plants "removes" the nitrates that would otherwise build up over time in the fish tank. We've known for ages in the aquarium world that we need beneficial bacteria to convert ammonia to nitrite and then nitrite to nitrate. However, the build up of nitrate has always been a "problem". If you add live plants to the equation that you harvest regularly, you are mitigating that "problem" to a large degree. The growbeds are also a biofilter themselves (massive ones actually), so will help keep ammonia and nitrite spikes in check as well.


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## Gizmo (Dec 6, 2010)

kellenw said:


> If you add live plants to the equation that you harvest regularly, you are mitigating that "problem" to a large degree.


How would harvesting a plant reduce nitrates? I might not be understanding you correctly, but I would think a fully developed fully aquatic plant would do a better job of mitigating nitrates than a plant that grows 50%+ out of water.


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## kellenw (Mar 28, 2010)

[email protected] said:


> How would harvesting a plant reduce nitrates? I might not be understanding you correctly, but I would think a fully developed fully aquatic plant would do a better job of mitigating nitrates than a plant that grows 50%+ out of water.


An aquarium is a closed loop system. You can't simply add fish food (nutrients) forever and expect the system to maintain a healthy balance. Ultimately, it will become toxic. The pH will become increasingly acidic and ammonia levels will eventually overwhelm the system's ability to "process" them into nitrate. In the meantime, nitrate will also continue to accumulate to the point that, it too, becomes toxic to the fish. This is why we have to do water changes. If you are removing nutrients (in this case in the form of live plants), you are breaking this cycle and keeping things balanced.

This is a really basic way to describe it, but plants "eat" nitrates and other trace nutrients as they grow. A plant (aquatic OR soil based) that remains in the system and is left to die and decompose releases these nutrients back into the system. When you harvest the plants, you interrupt this cycle.... and "remove" nitrates that are being "stored" in the plant in other currently more complex forms. Of course, you must have other plants that quickly grow to fill this void created by harvesting.

If you are able to grow enough aquatic plants in your system such that you can consistently harvest enough of them to control your nitrates, you are doing the exact same thing. However, the keyword here is HARVEST. Until you REMOVE the plant, the nutrients are still there.


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## Gizmo (Dec 6, 2010)

My main tank (see sig and side picture) currently has a high enough density of plant life that the plants consume all of the nitrates in the tank and I have to add additional nitrates via dry chem fertilization, along with potassium, phosphates, iron and trace elements to maintain healthy nutrient concentrations in my tank. I also inject CO2 and run a 48W T5HO. Needless to say, I have a veritable jungle in there. I'm also very well versed in decomposing mulm (fish waste) generating ammonia which is consumed by nitrospira bacteria and digested as nitrite, which is then consumed by nitrosomona bacteria and converted to nitrate. I also know that live plants love nitrate, but love nitrite and ammonia even better, because they are easier to break down for the nitrogen. Currently, without fertilization, in the course of a week my liquid test kits would yield 0 ppm ammonia, 0 ppm nitrite, and 0 ppm nitrate. This blew me away the first time I achieved those concentrations.

I've never heard of plants "storing" nitrate. Rather, I've heard of plants consuming nitrate, both from the water through their leaves, and through their roots buried in the substrate. I understand that decomposing plant matter, as with anything else decomposing in the tank, generates ammonia. What I don't understand is how a plant with the majority of its foliage exposed to air is supposed to mitigate any nitrates in the water. I understand that a large AP plant's root system would consume vast amounts of nitrates and other waste materials in the substrate, but in my opinion, a plant with only the stalk in the actual water would not consume nitrates in the water.

Maybe I'm missing the point here - is the advantage of an AP system to grow food for yourself, to grow a beautiful semi-aquatic garden, or to benefit a full aquatic system including a burgeoning fish population? If it is the former two, then I completely agree that an AP system is the way to go. However, if it is the latter - the full aquatic community - then I have to beg to differ that AP plants would benefit the tank over fully aquatic. Again, this might be because I'm missing something though.


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## kellenw (Mar 28, 2010)

[email protected] said:


> My main tank (see sig and side picture) currently has a high enough density of plant life that the plants consume all of the nitrates in the tank and I have to add additional nitrates via dry chem fertilization, along with potassium, phosphates, iron and trace elements to maintain healthy nutrient concentrations in my tank. I also inject CO2 and run a 48W T5HO. Needless to say, I have a veritable jungle in there.


That sounds like a lovely tank. Do you perform water changes? Do you remove excess plant growth regularly? Do you remove dead or decaying plants and leaves? If so, you are removing nutrients... the same as what an aquaponics system would achieve.



> I'm also very well versed in decomposing mulm (fish waste) generating ammonia which is consumed by nitrospira bacteria and digested as nitrite, which is then consumed by nitrosomona bacteria and converted to nitrate.


I believe you have it mixed around a bit. Nitrosomas bacteria utilize ammonia as a source of energy. They metabolize the ammonia and promote its oxidation to nitrite ions and water. This nitrite rich metabolic waste from these bacteria is then available as a food source for Nitrobacter bacteria. The Nitrobacter bacteria oxidize the nitrite ions to nitrate.

Also, mulm is not just fish waste in your case of a planted tank. It is considered to be all the organic debris (detritus).... decaying plants including.



> I also know that live plants love nitrate, but love nitrite and ammonia even better, because they are easier to break down for the nitrogen.


As I understand it, plants generally consume ammonium and nitrate readily. Nitrite and true ammonia consumption is largely plant species specific and in some cases is actually toxic to the plant, depending on concentration. It's been a while since the biology class days though.



> I've never heard of plants "storing" nitrate. Rather, I've heard of plants consuming nitrate, both from the water through their leaves, and through their roots buried in the substrate. I understand that decomposing plant matter, as with anything else decomposing in the tank, generates ammonia. What I don't understand is how a plant with the majority of its foliage exposed to air is supposed to mitigate any nitrates in the water.


Plants utilize nitrates for growth and respiration. Nitrogen taken up by plants is RELEASED as amino acids (organically bound nitrogen) when the plant's tissue is eaten or the plant dies and begins to decay, and thus, your nitrogen cycle begins anew. Remove plant... remove nitrate (it's just not in that specific form... yet)



> I understand that a large AP plant's root system would consume vast amounts of nitrates and other waste materials in the substrate, but in my opinion, a plant with only the stalk in the actual water would not consume nitrates in the water.


Part of this is explained through the process of mineralization and part of it is due to direct contact with the water itself. Researching aquaponics and mineralization will shed a lot of light on this for you.



> Maybe I'm missing the point here - is the advantage of an AP system to grow food for yourself, to grow a beautiful semi-aquatic garden, or to benefit a full aquatic system including a burgeoning fish population?


I kinda think you are. hehe....
You would have to ask the OP what his/her intent is. I was just answering a question and providing a definition of what he/she was describing when talking about combining fish tank water effluents and hydroponics.



> If it is the former two, then I completely agree that an AP system is the way to go. However, if it is the latter - the full aquatic community - then I have to beg to differ that AP plants would benefit the tank over fully aquatic. Again, this might be because I'm missing something though.


I wasn't aware we were debating this to begin with, but I would say yes, the decision of whether to implement or not implement aquaponics in an aquarium system would depend entirely on the goals of its owner.


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## Gizmo (Dec 6, 2010)

You're right on several counts - I do trim my plants and I do do weekly 50% PWC's. And though my reasoning for both isn't to remove nitrates (PWC's because I use the EI dosing method for my fertz and trimming to allow more light into the lower water column, being a tall tank), they have the effect of removing nitrates. I also mixed up the nitrifying bacteria's names, my bad. Thanks for the corrections 

And it also is a matter of preference on the AP vs. true aquarium. One thing I would assert, however, is that you cannot make an AP plant a fully aquatic plant - its leaves will melt away if submerged, and the plant will die.


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## beaslbob (May 29, 2009)

Just to throw a "cinch" in the gears

What you'all think about the concept is plant life "recycling" fish wastes?

After all I do no water changes, add not fertz or co2, do very little harvesting and (in my marine tanks) the fish are constantly eating the macro algaes and micros algaes.

So is it possible for plant life to recycle fish wastes into fish good?

my .02





my answer YES.*old dude


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## Gizmo (Dec 6, 2010)

beaslbob said:


> So is it possible for plant life to recycle fish wastes into fish good?


I think for the most part yes. Think of a pond - very little input from outside. But I also think you need to simulate certain environmental factors, the most obvious of which is extra feeding, lighting and heating, the more subtle of which would be water changes and/or topping off.


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## beaslbob (May 29, 2009)

[email protected] said:


> I think for the most part yes. Think of a pond - very little input from outside. But I also think you need to simulate certain environmental factors, the most obvious of which is* extra feeding, lighting and heating,* the more subtle of which would be water changes and/or topping off.




And more plants *old dude

*w3


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## kellenw (Mar 28, 2010)

beaslbob said:


> Just to throw a "cinch" in the gears
> 
> What you'all think about the concept is plant life "recycling" fish wastes?
> 
> ...


Hello beslbob,

To a degree, yes this is correct. Plants are part of the broader nitrogen cycle (perhaps nitrogen CIRCLE is more appropriate... hehe) in an ecosystem. However, when it comes to a fish tank, variables such as fish stocking density, plant density, algae type and density, daily feed rates, pH, dissolved oxygen content, temperature and many others come into play in determining just how long or consistently a tank can go without plant harvest or water changes before problems begin to surface. Remember, some of the nitrogen in the system is "lost" to the atmosphere. How much, I am not even remotely qualified to guess on.... hehe. However, theoretically, with very minimal inputs (fish food being the main input) and extremely low fish stocking rates, a planted system could possibly survive for quite a long period of time, maybe years, without any other human intervention. The problem is that most of us tend to stock our tanks with far more fish and feed far too much for a tank to self-regulate in any reasonable fashion.


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## beaslbob (May 29, 2009)

kellenw said:


> Hello beslbob,
> 
> To a degree, yes this is correct. Plants are part of the broader nitrogen cycle (perhaps nitrogen CIRCLE is more appropriate... hehe) in an ecosystem. However, when it comes to a fish tank, variables such as fish stocking density, plant density, algae type and density, daily feed rates, pH, dissolved oxygen content, temperature and many others come into play in determining just how long or consistently a tank can go without plant harvest or water changes before problems begin to surface. Remember, some of the nitrogen in the system is "lost" to the atmosphere. How much, I am not even remotely qualified to guess on.... hehe. However, theoretically, with very minimal inputs (fish food being the main input) and extremely low fish stocking rates, a planted system could possibly survive for quite a long period of time, maybe years, without any other human intervention. The problem is that most of us tend to stock our tanks with far more fish and feed far too much for a tank to self-regulate in any reasonable fashion.


Yeppers I do harvest plants (fw) and macro algae (marine).

So actually I do use export and recycling.

Just making a point here.

my tanks have ran for years (up to 9) with no water changes and a very heavy fish load. (in FW on the order of 20-30 plattys/guppies in a 10g including 6 or so reproducing adults, marine 6-8 fish including two two tangs (yellow, regal) in a 55g). With nitrates and phosphates unmeasureable.

So IME all this you have to export nitrates is non sense. when it gets a little crowded with plants I just harvest some. 

my .02


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## kellenw (Mar 28, 2010)

beaslbob said:


> Yeppers I do harvest plants (fw) and macro algae (marine).
> 
> So actually I do use export and recycling.
> 
> ...


Hi beaslbob,

I just don't think you quite understand the whole biological process here. At any rate, when you harvest plants (like you said you do), you are removing nutrients. In your case, it appears you are harvesting at a rate that allows your tank to remain in relative balance without the need for water changes. That's exactly the process we've been discussing. 

If you read back through the thread, you will find that this has been covered pretty thoroughly.

Now, if you use things like charcoal or zeolite in your filters, you are also removing nitrogenous nutrients "chemically" when you change this media out as well. However, that has not been discussed because it was not the OP's original question. I just thought I would add that for your benefit since you likely do utilize these materials in your system(s) and that might be leading you to believe there is more "magic" happening than there really is.


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## M1ster Stanl3y (Dec 10, 2010)

You don't know bob s builds...he doesn't filter. He def knows how to set up a planted tank and members are building off of his set ups and finding success...so I would guess he knows what he is doing


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## kellenw (Mar 28, 2010)

M1ster Stanl3y said:


> You don't know bob s builds...he doesn't filter. He def knows how to set up a planted tank and members are building off of his set ups and finding success...so I would guess he knows what he is doing



I just offered up a bit of advice IN CASE he was filtering and how it MIGHT be impacting his particular results, and it's really irrelevant to the discussion at hand anyway.... which I believe I made fairly clear.

I manage pond, aquarium, aquaculture and aquaponics ecosystems from 10 gallons in size all the way up to 14 surface acres in size. I also design commercial-scale mechanical and biological filtration systems. In addition, I am the hatchery manager for a mid-sized tilapia hatchery. I do these things for a living, and I too know what I'm doing.

I haven't once said Bob didn't know what he was doing or that he didn't know how to setup a planted tank, so I kindly ask that you refrain from putting words in my mouth. Now that we have that out of the way, relax and enjoy the thread.  Maybe we'll all learn something together. 

Fair enough?


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## Gizmo (Dec 6, 2010)

I say, to agree with both kellen and beaslbob, that if you have the right growth rate of plants and/or algae, in a tank without a filter or partial water changes, it is feasible (however, VERY hard to attain) a cycle where new plant growth and algae will feed a resident fish population, which in turn feeds the plants (without feeding or removing anything). I couldn't even begin to think of the plant selections, livestock selections, etc. that this would require, but this would serve to keep all of the nitrogen cycling through a closed system.

I've never heard of nitrogen gassing out of the water either. Guess you learn something new every day.


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## beaslbob (May 29, 2009)

Look I didn't mean to start a heated discussion. This does remind me of "flame wars" on other boards 2003-2005 or so. Especially with reef tank keepers. Back then it was all deep sand beds(dsbs) and the like. From what I understand the bacteria in the sand actually reduces nitrates to nitrItes and then to nitrogen gas. 

My main point here is just to emphasize the importance (as much as is possible) to establish a balanced stable ecosystem. but actually that could be more just an emphasis and in fact I could be actually exporting more then recycling.

But I do know that I routinely leave to a week or two and basically do nothing during that time. tanks do just fine while I am gone. 

I do feel that a lot of new people to this hobby have problems with the filtered/water change/chemical methods.

my .02


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## kellenw (Mar 28, 2010)

I believe we are saying more or less the same thing Bob. In a nutshell, plants (terrestrial or aquatic) provide balance. And there is more than one way to skin that proverbial cat.


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