# Is Substrate Fertilization Necessary?



## Mr Fishies (Sep 21, 2007)

Spawned from Starting a Planted Tank Part One, new thread to leave OPs journal intact.

Is Eco-Complete really complete? Is Flourite all you need? What's up with Mineralized Top Soil and Worm Castings under gravel. Are all those expensive Amano inspired ADA and Azooo additives that go under substrate necessary?

Years ago, having experienced dismal aquatic plant failures trying to stick plants in plain gravel I gave up on live plants. Tried again inspired by Diana Walstad's soil under gravel had great success. Currently I have a soil based tank and an Eco Complete, CO2, Estimative Index dosed tank. Which do I prefer?

In terms of work to maintain, the soil based tank hands down. It gets topped up with water and occasionally a little bit of trace ferts and epsom salts/Equilbrium for Mg and other minerals. No water changes.

In terms of appearance and growth for Aquascaping, the Eco tank wins. Eco complete tank gets CO2, KNO3, KH2PO4, CSM+B, epsom salts/Equilbrium and at least a 50% water change weekly.

Stem plants grow fine in both tanks, but Crypts, swords and anything that is a true rooted plant thrives in soil...that's what they live in in nature so there's no big surprise there.

The same crypts in the Eco tank need to have ferts shoved into the substrate near the base/roots or they just sort of stall and growth slows down, followed by tons of roots coming up and out of the Eco in order to grab nutrients from the water column. If Eco complete is complete, why is this the case?

The content, listed in descending order doesn't even mention Nitrogen or Phosphorus, and if it does supply potassium to plants, it's supplying almost 8 times more Iron! That's not good. If it was supplying everything plants need, NPK should be the first 3 items on the list, as it is, N and P are not even in the top 20 and K is 6th.

Long term, if plants are going to grow and create new tissue, the building blocks for plants and photosynthesis (NPK and Carbon) have to come from somewhere other than your substrate.

Content in PPM in descending order.

Aluminum - 43152
Iron - 41625
Calcium - 33066
Magnesium - 23116
Sodium - 12917
Potassium - 5296
Silicon - 4499
Titanium - 4487
Manganese - 976
Sulfur - 361
Barium - 337
Strontium - 278
Vanadium - 239
Zinc - 78
Chromium - 50
Cobalt - 33
Nickel - 33
Lithium - 8
Boron - 2
Cadmium - 2
* *plus others (NOTE: This is Carbisea's note)
*


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## Chris S (Dec 19, 2007)

I think you misunderstood what I was saying. 

I absolutely agree that eco-complete, or any plant substrate, does not properly supply the macro-nutrients used by plants (nor is it intended to). These must be supplied by other means, whether it be active fertilizing by dosing, or passive by the use of fish waste and food waste.

Plants can and do use seemingly "inert" substrate (rock/soil, whatever you want to call it) to liberate nutrients needed through. Plant roots are colonized by symbiotic bacteria that use acids and hydroxides (Potassium hydroxide typically I believe, but correct me if I am wrong). These actually break down the substrate and free nutrients that the plants use.

Use a garden for an analogy. If you provide fertilizer for it, it improves the growth. You wouldn't, however, plant your garden on pebbles just because you are fertilizing - you would use a "substrate", so to speak, that is appropriate. That said, you would still use soil to plant even though you aren't fertilizing.

Aquatic plants don't 100% feed from the water column, in fact as I mentioned, many are heavy root feeders.

With time, fish food, fish poop and other decaying organic matter, any substrate becomes and better source for N,P and K.


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## Mr Fishies (Sep 21, 2007)

I guess I might have misunderstood...but your statement that top soil was a bad idea because there were substrates available that were superior to the natural approach was misleading IMO. It sounded like you suggested one can buy a bag of gravel that doesn't need fertilization, that Eco/Fluorite were all in one solutions.

Which when you look at it, is kind of how they are portrayed by their respective companies with words like _"Complete"_ the name and marketing phrases like _"Flourite® never has to be replaced. It remains effective for the life of the aquarium." _and _"[Eco] contains all the mineral nutrients needed for luxuriant aquatic plant growth"_

The point of the top soil is to be a big store of slow release, organic nutrient for plants. Yes it's messy, especially when uprooting big plants, but I'd rather have low nutrient dirt stirred up in my tank than a less visible cloud of high nutrient root tab or plant spike...that's a recipe for algae.

As far as plants or symbiotic bacteria actively deriving nutrient from an inert substrate, I'm skeptical, plants typically are passive in their feeding habits. I'd still like to see a citation or link supporting the notion that plants can break down a substrate like Eco or Fluorite to feed themselves. I can't find anything to disprove the notion, I just can't find supporting info either. (BTW: Potassium hydroxide is a base, not an acid and it's a man made made inorganic compound.)

I don't believe that fish waste can be counted on to provide enough nutrient to keep anything but the lowest of low light tanks running, even then if plants will deplete a layer of soil under the gravel, how many fish and how much food would it take to keep the nutrients up?! A lot more than I have it seems.

BTW, this isn't personal, don't get pissed at me, I'm not trying to argue or pick a fight, I'm trying to educate myself (and anyone who cares to read this) on the facts and hopefully a reliable, easy means of augmenting/fertilizing my Eco Complete and there's no way I'm paying ~$1.25 each for root tabs!

So far, I'm was thinking Osmocote+ (which I, as a consumer, can't get in Canada, but 50lb bags can be purchased for agriculture...go figure), or something like the roll your own clay root balls the bhk99 (and others on various forums) are using. Being inherently lazy...err...I mean efficient, I was hoping to find something that required less effort though.


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## Chris S (Dec 19, 2007)

You are correct that plants typically are passive in the feeding habits, but this does not mean that the root structure, or the process in which they obtain said food is passive or simple.

Look up mycorrhizal fungi for example or:

Symbiotic bacteria: http://www.ctu.edu.vn/departments/dra/journal/inter/107.pdf

There is tons of stuff out there about it, most of it applies to terrestrial plants - so you have to wade through a hole bunch of stuff.

I'm no scientist, maybe someone else with a little more biology background than me can chime in!


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## Merman (Nov 23, 2009)

...you guys are sounding kind of 'heated' and I was just want to add my own limited two cents worth - I'm not high tech at all, no CO2, no expensive lighting: I can have tanks filled with various crypts, aponogetons (it's a bulb..like a tulip everthing they need is stored within), anubius, java fern and moss so I figure why bother, I'm pretty happy.

That being said I love to experiment and one thing I attempted was the use of Flourite, some of which I read said it had to be used exclusively unmixed with 'other' gravel/soil, etc. in order to work so I did just that, added soil/clay balls/peat to some, used clay pots full of Flourite......in my opinion - this stuff did nothing.

About the macronutrients (NPK) - they just simply have to be there in sufficient amounts. Adding micronutrients, special lighting, etc won't do anything if the NPK isn't there.

I don't believe fish/food waste supplies enough NPK for all plants - sure java fern, anubius are fine without it but crypts won't make it. I've been dealing with several tanks and just have not been willing to pour water column fertilizers in and then remove them with water changes (I do a lot) and watch my money go down the drain. 

I won't spend money on substrate fert tablets either, however have had great success with...don't laugh...and you've probably read it before...Jobe's spikes 16-2-6 for fern and palms...1.99 I think at Walmart for 30 spikes. I break each spike into thirds and insert every 6 weeks or so. I've had no trouble with water quality.

My crypts were growing like mad last year when I was using these then I stoppped putting them in for 6 months or so and growth in my crypts virtually stoppped...started using them again about three weeks ago and voila!!

No big explanations of chemical processes or complicated equipment here but just some food for thought....sometimes the answers are more simple than you think....hope it helps.


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## bae (May 11, 2007)

Everybody is right here! ;-)

There's always some limiting factor for plant growth. In a low to moderate light situation, with moderate stocking, and appropriate plants, the fish will fertilize the plants. They won't fertilize them very much, so growth will be relatively slow. This may or may not be what you want. If you add fertilizer, either to the water or the substrate, and the plants grow faster or better, the system was limited by nutrients. If you get lush growth of algae instead, the tank is probably limited by light instead of nutrients.

There are a lot of different equilibrium points in which the main factors for aquatic plant growth -- light, major, minor, and trace nutrients, and CO2 -- are in dynamic balance, the plants are healthy and growing, and algae is not a problem. The trouble comes when one of these factors is out of balance with the rest, or people try to grow plants that are not suited to their conditions.

Different people have success with different systems. There's no point in arguing with what works. When someone is new to the whole concept of planted tanks, it can be very confusing as to what is needed to have a healthy good looking tank. The answer is, as with so many things in biology: "It depends". You can go with the very high input Dutch aquarium system, e.g. Dupla and Dennerle. You can go with Walstad's system. You can go with the even lower tech 'system' I use. If you pick and choose bits and pieces from various systems, it can work too, if you understand what you're doing, or at least know when you've got a problem and what caused it. If you don't know what you're doing, or you can't identify problems and their causes, you can end up with an awful mess after spending a lot of time, money and effort, and conclude that planted tanks are even more complicated and expensive than reef tanks.

And of course, no matter what the vendor claims or implies, there's no magic product that will solve all problems and remove the need to think, observe, learn and understand.

As for plants deriving nutrients from mineral substrates, it does happen, but it may not be a fully effective source of nutrients in a planted tank. CEC (cation exchange capacity) is a metric of to what degree cations (potassium, iron, ammonium, etc) can be exchanged between soil particles and soil water. It depends on the particle size (surface area to volume ratio) and the mineral composition of the soil particles. Clays, with microscopic particles that are mostly extremely thin and flat, have a much higher CEC than sands, and can release potassium and other cations in significant quantity, as well as holding other cations in reserve, or sequestering toxic metals. Which cations are held or released depends on pH, and plants can use root secretions to alter the pH of the film around their roots to facilitate this. Symbiotic associations with mycorrhizal fungi and other soil organisms also work this way -- the roots secrete nutrients (sugars) that feed the fungi which help leach plant nutrients from soil particles. In wet or waterlogged soils they also carry oxygen into the soil to support these symbioses (as well as the functioning of their own roots.

As the original poster (in the other thread) found out the very hard way, a thick layer of organic matter will go anaerobic in a particularly revolting and unhelpful way. Walstad recommends ordinary garden soils, which seldom have more than a few percent organics, and recommends against peats and other organic ingredients. She suggests a layer no more than an inch deep under several inches of inert substrate. This controlled method provides good cation exchange, limits the problems of low pH which can release toxic cations from soils, and provides a mildly anaerobic environment which will reduce iron to the plant-available ferrous form, as well as reducing nitrate back to ammonia which is the preferred form of nitrogen for plants. Depending on its mineral composition, such a substrate can provide minor and trace nutrients for many years.

Humus is an organic material that is at the end of the breakdown process. It consists of the most rot-resistant portions of organic matter such as lignin from higher plants and the outer walls of microbial cells. It also has a good CEC. Mulm, the older the better, is basically humus. Before it gets to that point, it's releasing plant nutrients as it rots, and sequestering them in the same way clays do. So a layer of mulm, especially one that has worked its way down into the substrate, is similar to clay in its effect. If there are no rooted plants to bring oxygen to that level, and there's a lot of mulm that hasn't broken down completely yet, you can get a awful, highly reducing anaerobic layer at the bottom, emitting hydrogen sulfide, so you have to gravel vacuum to keep this from happening. On the other hand, if you do have rooted plants that like these conditions, the substrate will be healthy and the plants will be do well. Again, it depends on your system -- the parts have to balance.

I've never used a soil substrate, but now that I've got Walstad's book I'm eager to try it. I've had good results raising plants like vallisneria and crypts in plain gravel, in sand and in turface, which is a calcined clay, i.e. a red clay that has been fired to a hardness intermediate between flower pots and non-clumping cat litter. I've never used fertilizers or CO2, and I haven't needed to prune or thin rooted plants very often. I use low to moderate light (1-2 watts per gallon). In fry tanks, I use a lot of unrooted plants like moss and naias as well as floating plants. My system (if you can call it that) works effortlessly for me. Other systems work for other people, too.

A little to the side: If you want the benefits of plants as water purifiers, e.g. in heavily fed fry tanks or in tanks with large fish that will disrupt rooted plants, plants like naias, moss, and surface floaters like duckweeds and frogbit are excellent. They grow fast and really suck up nitrogen and other pollutants/nutrients. The provide cover that makes the fish feel more secure, and have a large surface area for desirable bacteria to colonize (as well as lots of tiny critters to feed the fry). It's no Dutch aquarium but it looks far better than a bare tank to my eye, and it's great for the fish.


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## Chris S (Dec 19, 2007)

Sorry, I hope I didn't sound heated - it isn't my intention to have anything other than a friendly debate here.

There is one more aspect of flourite/eco-complete I did want to mention though.

It has been stated here, and I agree with the fact that these substrates themselves are not a good source for NPK. What I think has been overlooked though, is one of the largest benefits from using these "plant" substrates, which is their ability to absorb and store even these macro-nutrients.

While they themselves are not a source, they do quickly become a source. Fish waste, food, dosing, root tablets - anything that adds the macro's can, and are, abosrbed into the actual substrate itself. From that point, it does become a source of NPK - and carbon. This is why I believe these plant substrates are great no matter what sort of planted tank you run - low-tech, high-tech, low-light, high light, etc. etc.

Still, I really can't disagree with bae, "_And of course, no matter what the vendor claims or implies, there's no magic product that will solve all problems and remove the need to think, observe, learn and understand._"

Wise words =)


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## Zebrapl3co (Mar 29, 2006)

Nicely put bae. Very good stuff. Thanks,

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## okoolo (Nov 1, 2009)

to be perfectly honest you guys just confused the heck out of me

I have eco complete in my new still to be finished 55g tank (4" deep) (2x54w t5ho, dyi co2) and I thought I don't have to add macro nutrients, and if I add a bit of water column fert( big al's multipurpose food supplement) that will take care of it..

now on the other hand I'm forced to rethink my whole approach

I'm actually considering buying a scale and getting some ferts from a local hydrophonics store to roll out pmdd. I'm also thinking of buying some kind of soil fertlization sticks.. 

I just don't know anymore


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## Mr Fishies (Sep 21, 2007)

Don't feel bad, it seems this is a subject that doesn't really get much discussion when people are talking about what to do when starting a new planted tank. Other than some books and articles the specifically deal with substrate fertilization methods, which often don't discuss water column fertilization methods, I don't recall off-hand a "getting started/how to" that mentions this aspect of plant keeping so I’ll try to offer what I’ve learned (and am still learning) with an invitation for critiques and additions.

I think it’s safe to say the answer to the question “Is Substrate Fertilization Necessary?” is: Yes. As usual there’s a “But…” How will you feed the substrate? What will you feed the substrate? When will you feed it?

It's a matter that should be addressed or decided upon early, as in before you buy substrate since one method/product maybe isn’t practical unless they go down before substrate; others work better with different substrates and can be adopted at any time but are more effective with some substrates than others.

Much has been written about what substrate has the highest (or lowest) CEC, it’s a subject I've seen beaten to death on other forums, but there seems to be little information for someone starting out (or even someone who has been at it for a while and struggling) about how the choice of substrate affects maintenance and how often and what to do to feed your substrate. What substrate fertilization method you choose to an extent drives the choice of substrate. Or vice versa, the gravel you already have or choose dictates to an extent what fertilization method might be best. Is it a specialized plant tank substrate, what size are the grains, and if it has high CEC or plain old pool sand or quartz gravel?

Eco Complete, Flourite, and other substrates from Azoo and Red Sea that have a high Cation Exchanage Capacity allow them to lock nutrients up quickly and slowly release them in the water surrounding the substrate and roots where it is absorbed by the plants. Dosing them selectively where and when needed with something like root tabs, Jobes’ spikes, clay balls with ferts incorporated into the mix, basically more concentrated chemical fertilizers seems to be the way to go. Why? Because the high CEC serves as a vault for the nutrients added in the form of chemical fertilizers which are very soluble and otherwise quickly absorbed into the water column.

Another option is to use a more nutrient rich substrate component such as topsoil, mineralized soil, earthworm castings (there are probably others in use as well) which will typically be the lowest layer of your substrate, most times an inch or less is recommended. With very rich additives, they can be mixed with the gravel you intend to use to “thin” them out and help add weight to keep them down when plants are being uprooted or moved. Over top of this rich layer a more typical gravel can be used, expensive high CEC gravel or cheaper inert gravel, which serves primarily as a cap to keep the nutrient rich organics locked down where the roots of plants can use it but out of the water column. Smaller gravels in the 2-5mm range seem to work best. Fine sand can be too impermeable a cap and not allow water and oxygen to flow in and out resulting in anaerobic conditions and gasses that can harm fish or plants. Too large a gravel will allow the rich sub layer to migrate up too easily and mix into the water. It should also be noted that after a few years or maybe sooner even the richest of substrate will eventually be depleted especially in a tank that has lots of light, high plant mass or CO2 injection.

There are also a line of products from ADA that quite costly and are not readily available here in the GTA. Since I have no experience with them so I can't speak to them, other than what I have read in US forums but they are part of a planned layered system that shares aspects of high CEC substrate with rich additives incorporated.

Regardless of the substrate and what you might include underneath it or push into it in various areas, fish waste and food will contribute some nutrient over time, but it can take months before any appreciable amount builds up depending on the fish you keep and how much they are fed. If there are a lot of plants in the tank, the waste and nutrients that do settle into the gravel will quickly be used up before any appreciable amount builds up.

So unless it's a low light tank, had very few plants, plants that don't require a lot of nutrient, has plenty of fish vs. the plant mass (or a combination of all 4) some form of external nutrient is almost certainly going to be needed before starting or during the life of the tank or both.


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## okoolo (Nov 1, 2009)

should I start fertilizing right away or should I wait a bit for the plants to settle a bit?

I also have a heavily planted 15g where nitrate level has been 0 for a while now .. I was thinking of adding KNO3 but wouldn't soil ferts take care of that?
(Or I could just overfeed and let nitrate rise a bit)

I haven't seen many discussions for beginners on water column/soil fertilizers either which is a shame..


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## Chris S (Dec 19, 2007)

It really depends on what you want to grow and how you want to grow it.

To simplify the thread for you:

Plants need macronutrients like nitrogen, phosphorus, potassium and co2.

They also need micronutrients like iron, magnesium, calcium and a long list of others.

To fully fertilize a heavily planted tank, you should be supplying each macro nutrient, plus micronutrients.

These then must be balanced with the amount of light provided to them.

If you are growing low-light, slow growing plants - you might not need to fertilize at all.

If you are looking to grow some high-light, hard to grow, nutrient demanding plants, or are looking for a very lush aquarium it will likely be necessary to provide high light, co2 and a dosing of macro and micro nutrients on a steady basis.

If you provide one macro-nutrient without providing all, you will likely see increased algae growth as you are limiting their growth.

For example, if you provide N, P and K steadily, but provide no co2, the lack of co2 will restrict the plant growth while algae will be able to use the excess N, P and K you are providing.

Going back to the discussion on substrate: Is it necessary? I think so, but like Mr. Fishies says - it is not the only thing necessary. You don't have to worry about the CEC or the specific way plants uptake nutrients to make a decision. 

I would also summarize it all and say try what you think is right, correct your mistakes, keep reading and asking questions, but don't get bogged down by the technicalities and specifics. Trial and error is how most of us have learned how to have successful planted tanks. You can only learn so must by reading, eventually you just have to make some mistakes for youself.


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