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What are the challenges and limitations of "no fertilizer" planted tanks?


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I've heard a lot about people setting up aquaria to function as miniature ecosystems that can function with few artificial inputs like fertilizer. This naturalistic approach to fishkeeping appeals to me a lot more than relying on expensive products, frequent maintenance, and "artificial life support" more generally. That being said, I think most aquarists with planted tanks use some kind of chemical fertilizer rather than relying solely on their water chemistry and fish waste. That makes me concerned about whether or not the "natural" approach is sustainable or so limiting as to suck the fun out of the hobby.

So, in your opinion or experience what are the challenges and limitations of trying to run a planted aquarium without using chemical fertilizers?

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great questions. the challenge is... balance. 

healthy plant growth cannot occur without all the necessary nutrients being present, and available for uptake. there will be a direct relationship (direct = linear in this case) between how much plant growth occurs, and how much nutrients are used. at one end of the spectrum, you have no live plants. the only nutrients required are for fish metabolism/health. a balanced fish food will meet these needs fully. at the other end of the spectrum you have a jungle scape: tons of plant growth. not just tons of plants, but plant growth. this will need large amounts of nutrients.

what you're asking is can those nutrients come from sources other than artificial fertilizer? The answer is yes, but those tanks are harder to set up, balance, and maintain. One option is "dirted" tanks. The right type of dirt under an inert substrate cap will be some kind of mineralized soil, which will contain the right balance of nutrients, that will be released to plant roots in the substrate over time. probably not great for high rates of plant growth, but suitable for low and medium growth. Walstads are a good example.

Another source is fish poop. Think aquaculture. dump in tons of fish food, it gets eaten and excreted, fish poop in water is a complete fertilizer, plants take it up. this works because the plants are effectively emersed. roots in water, leaves in air. high light and relatively high C02 (higher than in water) = high plant growth, that it turn relates to high uptake of the nutrients from the water. To make it work with lots of plants you need lots of fish food going in. That means lots of fish. So overstocking, without a filter. There's your challenge, FYI. 

So the question is, what are you looking to achieve? some plants? medium plants? densely planted? How many fish? lightly stocked? heavily stocked? How much light, and will there be CO2? What type of substrate? It's all related. 

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Time, patients & potassium would be your biggest obstacles. The next would be buying progressively advanced,
plants and livestock, else you will 'crash the system'.

For example, first microbes grow, then colonies of microbes, and eventually detritus forms. Undesturbed snails will slowly eat it, break it down, poop it out. Fast foward, then algae forms, again snails & microbes eat it & break it down, maybe a simple fish shows up to share in the algae. Then bigger fish show to eat the smaller fish. All the while simple plants live feeding off their predecessors nutrients (which were broken down by microbes and snails) then die being replaced by more advanced plants. Fish eat, poop and die, again microbes and the lowly snail 'chew' the nutrients up small enough for plants to absorb. For a truely 'natural' system you need the time to make enough 'substrate gravy' that an advanced plant can thrive off of.

Sure you can skip 10~20 years of natural ecology and just buy products to get a head start but eventually the system will demand more than can be quickly replaced. The biggest nutrient being potassium which isn't naturally present in water. It needs to be broken down small enough (chelated) for plants to absorb.

 

Edited by JoeQ
Added snail poop
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It sure does seem to engender a whole lot of interest on youtube…

 

no filter no fert no heater tanks with vibrant lush growth and algae free tanks. And lots of people also aim for the no water change issue as well…

I watched and re watched Foo The Flowerhorn 3 hour video where he kept and bred sparkling gourami and had amano shrimp multiple times.  Partly because I love Erik Satie Gymnopedia in the background.  
 

and afterwards I bought Diana Walsteads Ecology of the Planted Tank.

 

I bought Miracle Grow Organic Potting soil and pulled out an old screen window…

 

I did not strictly follow the plan.  Personally I have no problem with “chemical” fertilizers.  Flora and Fauna are both pretty detailed chemical manufacturing labs in their own right…. And if you want to raise calcium and carbonates in your tank, well you can buy a compound that you dose a known amount of calcium and carbonates or you put crushed coral in that adds calcium and carbonates and they slowly dissolve slowly raising tank levels over time.  And if you do a water change you impose a significant change until they slowly raise again…

As to price a bottle of Easy Green is 20 bucks and lasts me a long enough time for me…
 

I am not a fan of no water change as the water develops a tint I dont like.  And I find flow certainly helps to transport nutrients and flush away dissolved organics that Algae likes to feast on.  If I am going to move water I might as well move that water through filter media..

some people pull it off.   I didnt and I tried for about 8 months.  I was constantly battling Algae…

To my mind a no filter, no heater, no water change, no ferter,izer tank is no longer the holy grail to pursue…. But, that being said, there are a whole lot of ways to enjoy this hobby and if that challenge appeals to you and brings you pleasure, well, that is a win…

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Ok, noticed the heading.  Challenges and limitations…

in a low tech fert free tank you will struggle with low growth, and algae out competing plant growth.  Now it is certainly doable, but it is more of a challenge to find the correct balance.  And any change needs to be kept stable for a longer period to see the results.  In a non co2 tank it can take 6 weeks to see the same amount of growth that occurs in a co2 injected tank with high lights and high fertilization.  Plants continually reprogram themselves to optimize for existing conditions they find themselves in. This diverts energy away from growth. They do so predominantly in the new growth. In a low tech tank it takes longer for them to do so.

 

A Walstead  tank uses nutrient rich substrate to feed the plants early on that has a fair amount of wood fiber in it.  As the wood fiber decomposes it helps supplement CO2 levels in the tank.  Since plant mass is about 50% carbon, carbon limitation in an aquarium is a significant growth limiting nutrient.  Atmospheric air in a residence will be around 600 to 1000 ppm with windows closed and in a closed room with occupants can easily hit 2,000 ppm.  Outside we routinely see in the 450 to 550 ppm range.  
 

In an uninjected tank you will see roughly 3 ppm.  A Walstead tank hovers around 5-6 ppm IIRC.  An injected tank might get up to 30-35 ppm.  I keep Ludwigia repens in both injected high light, high fert tanks that grow 3-4 inches in a week, and also a low light no supplemental co 2 and moderate ferts where it takes 6-8 weeks to grow 4 inches.

The nutrient rich substrate depletes with time and the wood fiber fully decomposes. The theory and goal is that by that time, fish waste, mulm, plant waste enters the substrate replacing nutrients and decay continues to supplement co2.

One theory that seems to make sense to me is that decaying plant matter releases waste organics that Algae thrives on…I dont “know” that this is true, but my experience is that removing it from my tanks seem to reduce the algae I had.  Leaves that get covered from algae tend not to recover.  My best results is removing them and allow new growth to replace them. Removing them removes a lot of Algae that will not be able to get dislodges and recolonize elsewhere.   It removes shading of areas allowing more light to feed new leaves and it no longer slows flow, allowing flow to reach new leaves providing them with nutrients in the water column and flushing away waste products of plant metabolism…

You have limitations of the plants that can grow in an uninjected unfertilized tank. There are plenty to choose from, but there are undeniably plants that need co 2 injection and fertilization.

In the Foo the flowerhorn video I mentioned in prior post he originally planted 10 species of plants.  As the video progressed he had Hornwort, Guppy grass, and one other species of plant as well as floating plant dominating the tank as others were outcompeted…

I never could find balance in an uninjected tank at first.  I went 8-10 months and then started with CO2 injection and started finding thinks getting much easier, and I learned more and honed my skillsIMG_2617.jpeg.facf207b5766ca988d65be1028050aab.jpeg

 

After a year of maintaining CO2 injected tanks free of visible Algae with good growth I decided to try the non injected tank again.  I started a 17 gallon fish bowl using under gravel filtration with baked clay substrate in mesh bags and mesh bags of aquasoil under an inert coarse black sand.IMG_2619.jpeg.4075585b8bc1ed17a0547da22afc0fc0.jpeg

fertilization levels are much lower than other tank and lighting is much dimmer. I still supplement with Easy Green fertilizer, and have a heater and air driven filtration.  I added a Lees triple flow box filter with gravel to weigh it down and polyfill for mechanical filtration as I was struggling with detritus on the coarse sand and hair algae growth before I added it.  I keep the nitrate levels at about 10-15 ppm in this tank and have successfully kept it free of visible algae for several months now. I do weekly 50% waterchanges.

 

I dont ever forsee eliminating fertilizer or forgoing water changes as I just dont see much benefit to doing so, the cost and effort ore relatively insignificant to me and much less than manually cleaning algae…

As mentioned potassium is a nutrient that is not going to be found in fish food, fish waste also.  

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So I just set up a tank with a fertilized substrate (1 to 2 inches) and a 2 inch sand-cap.   And I heavily planted it.  And the tank did great for a few weeks and then crashed really hard and I had to reevaluate what my system was actually doing and do a big reset:

1) Lights - dont go with low lighting.  Get some extra lights from day 1 and put them on a timer.  Max 8 hours, then make sure your tank is dark (not necessarily pitch black) in the interim.   This is worth EVERY penny.  Light is absolutely the key ingredient driving all of the plant-based chemical reactions, so there you have it.   We are doing photochemistry.  

2) Liquid Fertilizer:  Father fish calls this stuff "poison" which is just factually incorrect and entirely dogmatic.  FF says to plant the roots into the sand only, and let them grow down as they need.  Sure, that's fine in the long run, but unfortunately in the short term your plants are likely going to get outpaced by algae and then your system crashes.  Use liquid fertilizer to give your plants a boost in the time while they are establishing themselves.  Once that happens, you can slow down or possibly even eliminate water column additives.  But until then... my experience is you absolutely need to give your plants that boost.   And here's the cincher on this: you absolutely MUST heavily plant your tank from day 1.  You need a huge plant biomass, or you are going to have problems.   And the more plants you have, the more nutrients they require.  So give them a green boost.  

3) "Do Nothing"  -again, more "naturalist" dogma.  If your plants are dying off, you need fix the underlying reasons AND you need to remove a large part of the dying tissue.  Otherwise, that triggers more algae and more die-off and you have a positive feedback mechanism that ends up strongly favoring a primordial soup instead of a healthy fish-filled ecosystem.   So tidy up your tank and keep a hand on that balance scale, keeping it in favor of your plants and away from excessive algae growth.  At the same time, dont try to sterilize your tank of algae - in this respect FF is correct, some algae is good as part of a healthy ecosystem.

4) Carbon.  I added rotting woodchips to my substrate.  In my haste, I forgot to add a layer of crushed charcoal and wood-ash.  I really, really wish I had remembered to do this.  Rotting wood adds CO2, but the charcoal and potash is just like putting an afterburner on the process.  Plants LOVE this kind of thing.  At this point, I am looking at adding a CO2 injection bottle like in the Ocean Aquariums shop in San Francisco, but am unsure if my tank circulation is too high.  Worth a try, as while my plants are growing and establishing themselves, its clearly slower going than what I see in higher-tech tanks with increased CO2.   That said, at the same time I do like having high aeration, so it gets tricky here to balance things.  Again, this is another reason I really wish I had remembered to add a layer of charcoal to my substrate -just under the sand where the plants can quickly reach it.  

Anyhow. I am new to this, but that's my educated take on it, combined with my own experience so far, running a heavily planted, fertilized substrate + sandcap 50 gallon fish-in tank, including a small (20% of tank bottom) UGF with a powerhead for flow.  

Edited by daggaz
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On 6/10/2024 at 1:03 PM, TOtrees said:

So the question is, what are you looking to achieve? some plants? medium plants? densely planted? How many fish? lightly stocked? heavily stocked? How much light, and will there be CO2? What type of substrate? It's all related. 

I'm trying to set up a rack of very low maintenance mostly self-sustaining ecosystem tanks for colony breeding guppies so I can develop my own strain. I'm willing to make concessions on stocking rates for either plants or fish, but more of both is preferred where possible. I'm interested in minimizing expense, reliance on technology, and obligatory maintenance. I'm fine with working on the the tanks, I just don't want to have to.

So, no CO2. Substrate would be dirt from my backyard capped by coarse sand/fine gravel from the creek behind my land.

Edited by saint_abyssal
getting used to interface
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I would set it up as you describe, and then let the tank and/or plants tell you whether they need supplemental fertilizer or not. 

I think it will be hard to avoid, since you have competing or conflicting objectives. If you want to breed/raise guppies, you want the babies to turn into adults within a reasonable amount of time. That means feeding the tanks lightly is out of the question; you'll be feeding medium or heavy. That means water changes. "Can't I get the plants to clean the water?" Sure but then you need to support high numbers of plants, and strong plant growth. That requires the right plants (not demanding of CO2), and a decent amount of light. If you don't want densely planted tanks, then the plants can't do the water cleaning for you (at least not on their own). If you have densely planted tanks, it's unknown if you'll need supplemental ferts or not. My bet would be yes you probably will. 

You might consider marine salt, at very low levels. I think @Cory is generally a fan of this approach. It's certainly compatible with guppies. 

You said you want more of both (fish and plants) if possible. The ideal scenario for self-sustaining is lots of plants and fewer fish. Fewer plants or more fish both pull you away from the self-sustaining scenario. 

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On 6/12/2024 at 12:09 PM, TOtrees said:

"Can't I get the plants to clean the water?" Sure but then you need to support high numbers of plants, and strong plant growth. That requires the right plants (not demanding of CO2), and a decent amount of light.

I've compiled a list of "species of interest" that are supposed to be pretty easy to care for.

Surface floaters: Water lettuce (Pistia stratiotes) and red root floaters (Phyllanthus fluitans).

Background plants: Yellow Flame Bacopa (B. caroliniana), coontail (Ceratophyllum demersum), Elodea canadensis, and Leopard Vallisneria (V. spiralis).

Middle to back: Dark Red Ludwigia repens and red tiger lotus (Nymphaea zenkeri).

Midground: Lesser creeping rush (Juncus repens) and Pink Flamingo Cryptocoryne wendtii.

Fore-to-midground: A blue cultivar of Bucephalandra, Pink Cryptocoryne becketti petchii, and narrow-leaved arrowhead (Sagittaria subulata). Foreground: Banana lily (Nymphoides aquatica).

  Are these good candidates for "the right" plants for my desired approach?

On 6/12/2024 at 12:09 PM, TOtrees said:

You said you want more of both (fish and plants) if possible. The ideal scenario for self-sustaining is lots of plants and fewer fish. Fewer plants or more fish both pull you away from the self-sustaining scenario. 

I'm okay with "fewer" fish, depending on what that means. Is there a ballpark way to quantify this? Maybe in terms of the old inch per gallon "rule" (eg this approach might support a half inch of guppies per gallon or quarter inch, etc).

 

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On 6/12/2024 at 5:01 AM, daggaz said:

2) Liquid Fertilizer:  Father fish calls this stuff "poison" which is just factually incorrect and entirely dogmatic.

father Fish makes a fair number of similar inflammatory comments…

On 6/12/2024 at 5:01 AM, daggaz said:

Carbon.  I added rotting woodchips to my substrate.  In my haste, I forgot to add a layer of crushed charcoal and wood-ash. 

You can easily enough add activated charcoal after the fact.  I have excavated capping a bit and placed items down there and recapped…. And I mention activated charcoal as the process of activating expands lots o nooks crannies and channels in it.  Great for harboring various beneficial bacterias, not just nitrifying bacterias…

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On 6/12/2024 at 12:18 PM, saint_abyssal said:

What kind of time table do you recommend for this process, or are there "signs" in the tank that it's ready for the next phase of succession?

I don't think there is a time table for a totally natural tank. This would take far more time than your lifespan allows, and suck the joy out of the hobby! I myself like to go as natural as possible (within limits) & let nature do most of the work! For this IMO you have to progress sloooooowly at the start.

Let the tank not only cycle, but then allow it to mature with a few plants and a cleanup crew. Let the detritis build up, the snails will eat it and poop it out; essentially making new dirt. Let the algae grow, resist the urge to scrape it, let the cleanup crew do its thing. Grow your ecosystem, understand this is the tanks foundation; its awkward teenage year. Its going to happen weather you interven or not. IMO constantly micromanaging this stage makes it worse!!

Id let this period go for 6 months to a year. Take this time to concentrate on your water quality, flow, aeration, ect. Maybe add a few guppies to stress the system,  and grow your bio load.

Now heres my limit, fertilization! Contrary to FF, fertilizer is not poison. Not when adding the proper doses and doing simple routine maintenance on a regular basis.  It is side stepping the slow process of letting nature break down organics/animals and minerals so other progressively more advanced species can live.

From this point you can add more advanced plants, preferably lots of them! But if you are not fertilizing them, doing water changes, routine maintenance, ect (simulating nature) algae will over take your aquarium.

Thats not saying you won't have some. Algae is incredibly healthy for an eco system. But having a robust cleanup crew and the time you took to grow your ecosystem should help reduce the manual labor involved.

Thats what I mean by natural aquarium, letting  nature take care of what can be resolved relatively quickly. But intervening with things that take decades to happen. Like organics breaking down small enough to feed other plants.

I wouldn't say there are signs to progress. My first post was mainly showing how excruciatingly slow a completely natural environment grows into a pristine aquatic environment.

As mentioned above Diana Walsted book is an excellent read and will give you a great prospective why a 100% natural aquarium is unrealistic.

Edited by JoeQ
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On 6/12/2024 at 11:17 PM, Pepere said:

You can easily enough add activated charcoal after the fact.  I have excavated capping a bit and placed items down there and recapped…. And I mention activated charcoal as the process of activating expands lots o nooks crannies and channels in it.  Great for harboring various beneficial bacterias, not just nitrifying bacterias…

Well my tank is heavily planted, on top of all the hardscape, so excavating is no longer an option.   Also not to sure how well my fish friends would like a cloud of sediment and bacteria in their water column.  Next time I set up a tank, I am really going to take it slow during the planning-to-hardscape phases.  I will also try the Barr "dry-cycling" method; I would love to start with a thick established carpet of foreground plants.  

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On 6/12/2024 at 6:30 PM, saint_abyssal said:

I'm okay with "fewer" fish, depending on what that means. Is there a ballpark way to quantify this? Maybe in terms of the old inch per gallon "rule" (eg this approach might support a half inch of guppies per gallon or quarter inch, etc).

I'm admittedly new to this (so feel free to correct me if I am wrong), but extensive reading gives me the following understanding:

1) You need a lot of plant biomass for a "natural" tank, natural meaning somewhat self-sustaining.  You will always be adding food (if you have more than a few small fish) and removing waste, the latter perhaps only in plant clippings, but it must be done.  

2) Bio-filtration is extremely important regarding how many larger aerobic organisms (ie fish) you can keep.  Surface area is key.  This is going to be your filter system, and in a dirted tank, the substrate itself after some time, and the surfaces of all your plants and hardscape.  If you have a larger filter, you can do more.  So an external cannister or even better, a sump, are going to really expand your capabilities.  Another good option is a UGF which has a huge, in-tank surface area and cant ever leak  -but you have to be tricky to set one up in a dirted tank. 

3) Plants need CO2.  Fish need O2.  This would seem like a simple situation but its not, due to two problems: a) the equilibrium concentration (natural amount) of the two gasses in water is not anywhere near the same, strongly favoring oxygen.  And to a lesser degree b) plants transpire at night, meaning they absorb O2 instead of releasing it.  What this means is that if you have a lot of fish, you really need a good oxygen supply.  But anything that puts oxygen into your water, will remove excess CO2, and this will start to strongly limit plant growth. 

So basically, you can have a lot of fish and a few plants, and its not a huge problem but its nowhere near to a natural system.  Or you can have a lot of plants, and a few fish, also with no big problems.  But in this latter case, as you add fish, you will push things out of balance.  If your filtration isn't up to par, you can get too much waste and this will poison your fish and potentially cause an algae and/or a bacterial bloom, also detrimental.  If there isn't enough oxygen, your fish will start to gasp, so then you up the aeration, but then your plants start to suffer and algae potentially takes over..  it becomes a tenuous balance.  

The advice as I understand it is to start with all the plants, add a small amount of fish (well under the 1 inch per gallon rule to begin with), and if you really want a good ecosystem, dont forget microfauna and other things like snails and detrivores.  Then when things are running smoothly, add some fish in small amounts.  See how it runs.  If your water remains clear and the fish aren't gasping at the surface, add a few more.  When you run into problems, you either need to rethink your filtration, or cut back a little on the fish.    When considering fish, keep to small fish.  Its not so much the length of the fish, but its overall mass that is important.  Big fat fish poop a lot.  Tiny nano-fish are a blip on the bio-load radar.  

And all of this on the caveat that with a new tank, you're going to have trouble keeping it stable.  The tank doesn't just need to cycle, it needs time to become seasoned -where all of the organisms are very well established.  

Edited by daggaz
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