How to Fertilize a Planted Tank (Rev 1.2)

[Avalon]

For quite some time, I've experimented with different fertilization methods in order to achieve the optimum balance for a planted tank. I've followed the two main methods currently available: the PPS (Perpetual Preservation System) and the EI (Estimative Index) only to realize these methods aren't for everyone, and some folks require a tailored method for their own planted tank. The aforementioned methods can certainly work for many, but they lack consideration for what the aquarist is actually trying to achieve. I've studied some great planted tanks and their owner's approach towards their fertilization regimen, and I've found one thing in common: minimalism and consistency.

Thus I propose a new method; one that is relies upon the tailored needs of each tank and is based on such. This method and article requires the basic knowledge of nutrients necessary for the planted tank, and focuses on how to implement them in a specific tank. Such basic information is readily available, so I will not elaborate upon it. I will make no bones about it: this method will require time, patience, and observatory skills. It will require some testing in order to recognize trends in nutrient use, but for the most part, testing will be minimal. Our focus will not rely upon nutrient levels as a gauge, but primarily the plants and their proper growth.


Table of Contents:

Post 1
Introduction



Starting Fresh

1. Starting a New Planted Tank
2. Resetting an Existing Tank
3. Keeping it Clean

Post 2
Fertilizing to Suit



Trace Nutrients

1. Iron

Macro Nutrients

1. Nitrogen
   Post 3
2. Phosphorous
3. Potassium

Introduction

You will need to understand a few "basics" in order to get started. This article is geared towards a planted tank that implements the use of carbon dioxide (CO2) injection and moderate to higher lighting, but is certainly not limited to these light conditions. It is not necessary to have very high light, but rather light that intense enough to adequately penetrate to the bottom of the aquarium. This method will compensate for the lighting on each tank. However, I highly recommend the use of a pressurized CO2 system, or at least the adamant control and use of DIY, as you will soon see the extreme importance of a stable source of CO2.

You will also need to know your tap water's parameters such as KH and GH. The pH of your tap water is not all that important, but it is good to be aware of it when acclimating new fish to your tank. KH (carbonate hardness) can play a significant role in the types of plants you wish to grow. For example, certain soft water plants will not grow well in water with a high KH. While most plants can thrive in any water, growing Rotalla macrandra in a KH of 15 degrees will not work. However, the common Amazon sword plant will do very well. The composite GH figure is not very important as a whole. In very high light conditions, you will need to know the levels (and ratio) of Calcium and Magnesium of your water. Ideally, a 2:1 (calcium:magnesium) ratio is ideal, but if it's a little off, that's ok. You can obtain all of this information for free by contacting your local water department and asking for a water report or by viewing it online at their website if they have one available, or simply by speaking to a representative. Why not test it yourself? Because their test kits are better than yours.

Starting Fresh

When beginning this regimin, or any for that matter, it is important that you start out on a clean slate. Muddled up water will lead you astray every time, and you will never be able to draw accurate conclusions. The goal here is to minimize extraneous variables. If you are beginning a new tank, then you will be starting fresh. If you are struggling in your current attempt at growing plants and find algae easy all too easy to grow, then you will find the following steps useful.

Starting a New Planted Tank

1. Have ALL equipment ready to go. This includes the filter(s), heater(s), lighting, substrate, CO2 system, and most importantly, plants--and plenty of them. Don't be scared; plants are your friend. They don't like to be alone and prefer lots and lots of friends (plant heavily!). The use of activated carbon in your filters would be a good idea for a while.

2. Set up equipment. Have it ready to plug in/turn on, substrate layed out, hardscaping set, plants ready to plant. Fill tank enough with water so that you can easily plant. Plant all plants. Fill tank the rest of the way. Turn on all equipment.

3. Allow 2 days to establish proper temperature and CO2 levels. Light duration should not exceed 12 hours (10 is adequate in most cases). After the third day, perform a small water change, 20%, using a hose small enough that you can suck any debris from the substrate (such as Flourite dust). Do not disturb the substrate by poking into it.

4. Three days later, do another small water change. The idea here is to prevent any kind of nutrient from building up. Do not disturb the substrate, filter, and do not bother the activated carbon (if used).

5. Repeat step 4 until you begin seeing new plant growth in the form of new, submersed leaves. You should begin removing old, emersed leaves before they decay. You should also now add algae eating fish/critters such as otocinclus catfish, SAE's, and shrimp. They are not required, but can help.

6. Keep doing the water changes until you notice plant deficiencies (pale leaves, veining, pinholes in leaves not due to fish, etc.). At this time, you should have a trace fertilizer ready. Also, you should have a Potassium (K) fertilizer on hand. We want to keep N & P out of the water until absolutely needed. Read on to find out about fertilizers. You will want to dose every other day, in small amounts. Do NOT fertilize before your plants show deficiencies!

7. It's now time to clean the mechanical media portion of your filter. If using power filters, you will need to keep the water changes up. These filters usually require an entire cartridge to be removed and replaced, thus eliminating much of the needed bacteria. If using a canister, clean the mechanical media and/or filter pad. Do NOT clean any dedicated bio media you may have. Perform the water change (both filter types) after the cleaning of the filter. Canister filters have a nasty habit of spewing out debris when started again. We are in a transitional period. Until the plants can fully sustain themselves without the presence of algae, they need all the help they can get.

Resetting an Existing Tank

1. Remove all plants, prune/remove all algae and infected leaves. Place them in a container with no water. Scrub the tank glass, silicone, equipment until it looks like new. Leave the filters running while you do this. Do NOT disturb the substrate. We want to prevent disturbing any and all bacteria.

2. Allow some time for the filters to pick up mulm and debris, while allowing the rest to settle. When the water is clear again and the debris has settled, use a hose small enough to suck the debris & mulm from the top of the gravel while only allowing for a 20-30% water change. Leave the filter(s) running if possible to capture any extraneous debris.

3. Replant the tank, minimizing the disturbance to the substrate. A mild harrowing of the substrate is ok, just don't go digging. Utilize a UV sterilizer if you have one. Refill the tank. Do not fertilize. Add activated carbon to your filters if possible (optional), but do NOT disturb or clean the bio media. We do NOT want to disturb the bacteria! Your filter flow may be reduced, but that's ok. We'll get to that later.

4. See step 4 above, skip step 5, and eventually continue to step 6 & 7.

Keeping it Clean

After having set a course to a "clean" tank, our goal is to keep it that way. Build-up of any kind is bad. No excess mulm, no excess nutrients, no excess debris, and no dead spots. When a planted tank is kept clean, it's far easier to maintain. It also substantially reduces the amount of wastes which can lead to the fouling of the water and excessive algae growth. While excess nutrients such as nitrogen, phosphorous, and potassium do not actually contribute to algae growth, saturated waters do not help matters. Remember: minimalism and consistency are the keys.

When beginning a planted tank, it's usually a good idea to utilize fast growing plants in order to keep the consumption of nutrients high. This helps stave algae off. In an established tank with slower growing plants, it's important to keep a clean environment so that nutrient build-up does not occur. In most cases, as long as water conditions are stable and plant growth is positive and stable, algae will not be a problem.

But how does one go about choosing the right fertilization method for his/her tank? Let's start by choosing the right fertilizers and following up with the right amounts.

[Avalon]

Fertilizing to Suit

We should start by choosing the overall plant growth rate of your particular tank. Stem plants are usually fast growers, while rooted plants tend to be slower growers. You will need to find out how fast your plants can grow! However, total plant mass and health have a significant impact on nutrient demands. I personally believe that it's too difficult to differentiate between growth rates of plants, but when plants are healthy, their uptake rates can really suprise you! When factoring in lighting, which acts as a catalyst for plant growth, it makes every tank different--while a certain plant may grow quickly for a few people, that very plant may grow much more slowly for others.

Let's view fertilizers like this: macro and micro. Micro is usually used minimally, while macro is used in much larger proportions. It also makes sense that when dealing with larger quantities/proportions, that larger problems may occur when dealt with improperly. So that's why we begin our fertilization methods with microelements, or "trace" fertilizers. We will also start out with the lowest dosages possible for the particular tank we are using. Everyday studying (i.e., relaxing) should be done in order differentiate between a plant doing well and one that has deficiencies. When sustaining plants only on water changes, CO2, light, and trace nutrients, it allows the aquarist to determine the contributions of the fish, their food, and their wastes. We can always attribute a certain amount of Nitrogen and Phosphorous due to fish food and their waste. When dumping in nutrients like they're going out of style, we aren't able to determine the effect of the fish, their food, and their waste. In a slower growing tank, this may play a critical role, but in a fast growing one, food and waste may be insignificant.

In essence, we want to test the waters...we want to give our plants and inch and let them try to take a mile. We will rely on a clean tank/water and the absolute necessities such as fish food (and their byproducts) to help the plants. We will progressively give the plants more trace elements. Eventually, we will begin to observe what our tank is not providing enough of (macro nutrients). After progressively increasing trace nutrients with no more positive results, it's time to turn to macro nutrients. Usually, algae will show up at this time, but in very lean conditions, we will have very mild algae issues. When a tank is saturated in one or more nutrients, it will be saturated in algae as well.

Trace Fertilizers

There are many to choose from, but for simplicity's sake, I prefer only two: Seachem's Flourish and Tropica's Plant Nutrition Liquid (PNL) because they are the most comprehensive on the market and both are priced well. Furthermore, these two fertilizers are separated by notsomuch as their chemical make-up, but rather their chelators (the agent that binds their elements together). Flourish uses more of an "organic" approach, and uses a relatively weak chelator. This means that plants can uptake the fertilizer faster, but the nutrients are not made available to the plants for quite as long. PNL uses a stronger chelator, meaning that while the plants cannot uptake the nutrients as quickly, the nutrients are made available to them for a longer period of time. Technically speaking, I would recommend Flourish for tanks dosed daily and soft water, while I would recommend PNL for slower growing tanks and/or hard water. Overall, I prefer PNL.

Iron

Iron (Fe) plays a large role in aquatic plant health and coloration. Usually in a high-light, CO2 injected tank where trace elements are added daily or semi-daily, you may find that there is no additional need for Iron. A lack of iron will be noticed in the form of pale plants. For example, hairgrass should be a medium-to-slightly dark green coloration when provided with enough iron. Hairgrass that is very light green in color, maybe with a yellow sheen, would indicate a lack of iron. The common sword plant (E. blehri) that lacks deep green leaf coloration indicates a lack of iron.

Again, there are two major forms of iron for the aquarist to choose from: Ferrous (Fe+2) and ferric (Fe+3). Iron in the ferrous state is much more easily taken up by the plants, and is the preferred form. Both Flourish and PNL use iron in the ferrous form, but as previously mentioned, they are separated by their chelators. Flourish uses a gluconate based chelator, while PNL uses a DPTA chelator. A weak chelator is ideal for the plants, as the iron would very readily available to the plant, but does not remain available to the plants for long--probably no longer than 8 hours. This type of iron would usually need to be dosed daily in order to have the greatest benefit. When dosing iron with a stronger chelator such as iron DPTA in PNL, the iron will be harder for the plant to use, but it will remain available for a longer time. This should be taken into consideration when accounting for your dosing habits. Iron in the ferric state is a little more rare, but will usually be found in dry iron supplements. I will not cover this type of iron for now, as for the average plant keeper, it's not as practical. Regardless, Iron is the biggest "little" element of all traces, and plays a vital role in the overall health of your plants and their vibrancy.

Macro Nutrients

Macro nutrients are referred to as such because they are used in the largest proportions in plants. They are Nitrogen (N), Phosphorous (P), and Potassium (K), or NPK. Nitrogen is by far the most used, with Potassium coming in second, and Phosphorous coming in last, but definitely not least. When plants are depleted of any of these nutrients, their growth will slow to a crawl, and the tank will result in algae growth. They can be purchased in liquid forms, but considering the dosing frequency in high-light CO2 injected tanks, and larger tanks in general, they are not the most cost-efficient form. Dry fertilizers are the widely becoming the most common form because they are the cheapest and many are combinations of the macro elements such as KNO3 (it provides K & N). Many chemical compositions are available.

Before getting into details of NPK, it's important to know what you are working with. By this I mean that when using tap water, you should know what's in it. Varying levels of each nutrient will exist in each individual's water. Once again, we will refer to our water report. Minimal levels will not be a much of a factor, but excessive levels may play a significant role in tailoring your fertilization needs. The most common problem would be excess levels of Phosphorous, but some may find Nitrogen an issue. Phosphorous is commonly added in urban areas to prevent pipe corrosion, but in rural areas, it may "naturally" occur from agricultural run-off. Be aware of what's going on in your area!

Nitrogen

Nitrogen, the staple of all plants--it helps the plant produce enzymes, proteins, and amino acids. It alone will have a significant impact upon plant growth. While nutrients such as P or K can hinder growth when limiting, a lack of Nitrogen will effectively halt growth and encourage plant decay. Fortunately, N is easily added. There are two types: Dissolved Organic Nitrogen (DON), and Dissolved Inorganic Nitrogen (DIN). DON is produced as you might guess, by bacterial oxidation from ammonia, resulting in NO3- from NH4+ (ammonia). DIN is your typical fertilizer supplement, such as from KNO3.

There is a significant difference in how the two types must be interpreted. It is fairly common knowledge that plants will use just about any form of N, if necessary, such as ammonia (NH4), nitrite (NO2), & nitrate (NO3). We think of this as the nitrogen cycle, and consider fish food/waste as plant food. However, in a high light, CO2 injected tank, this form (DON) of nitrogen is rather insignificant, and should not be relied upon as a significant source of N. It may play a more significant role in a low light planted tank with no CO2 injection. While plants may absorb DON, this is not a free pass to heavily stock fish, as you shall see.

Some sources may say that plants prefer ammonia, but this is simply not true per say. However, algae love it. It should also be known that algae can react far faster than plants to nutrient conditions. If you happen to have a condition where the production of NH4 is higher than the rate of oxidation by the biological filter and plant uptake, the result will be a constant excess of NH4. This excess NH4 will trigger algae growth in a matter of hours, and usually result in a major outbreak--most noticeably green water. The excess of NH4 does not need to be measurable, and in most cases, it isn't. Algae do not need much at all! This is one reason that using plant sticks such as Jobes or Miracle Grow are not recommended, as they contain high levels of NH4. This is also the reason that canister filters are recommended for the planted tank. Keeping a substantial harbor for bacteria will keep NH4 at bay. While they may not provide immediate bio-filtration "protection," they can easily compensate for fish growth and increased wastes over time. Power filters are notorious for their lack of biological filtration capacity, and are discouraged as the sole filtration method.

In a high light, CO2 injected tank, it is a given that DIN sources will be used. The most common is KNO3, because not only does it provide N, it also provides K! It can be bought as such, or is most commonly sold as "Tree Stump Remover," by Green Light. Plants will readily use this source of DIN without reserve. Another benefit to DIN is that it does not promote algae growth, unlike NH4. However, excessive levels will harm fish/shrimp, but these harmful levels far exceed this dosing regimen's requirements.

[Avalon]

How is it that you know you have enough? There are several ways to tell. First, you should know from the start what your N levels are from the water report. A heavily planted, extremely fast growing and highly optimized tank can suck up about 6ppm of NO3 per day. On average, you can figure about 2-3ppm per day if your tank is growing well. If you have the light, proper CO2 levels, good trace dosing, and your plants are at a standstill, a lack of N may be a problem. If you have colored plants, their coloration will be affected, and their color is largely dependent upon N. A lack of N will result in the plant not being able to provide enough chlorophyll to plant leaves, resulting in a deeper shade of red/orange/pink/etc. Many plants, such as Ludwigia repens, are mostly "green" plants with very soft hues of color. A lack of nitrogen will provide them with their intense coloration. This is not always a good thing, because it's an indication of N starvation. The use of a plant like this can be very useful to provide a visual indication of nitrogen levels. Unlike test kits, the plants will never lie. Another way would be to calculate your N dosing by using dosing calculators and estimated uptake rates. Begin conservatively, and gradually increase dosing rates to find a point where extra fertilization has no effect, then back off until there is an effect, and gather an average. Week-long increments of a particular (set) dosing rate should be used. I will elaborate on this later in this article.

Phosphorous

Phosphorous (P) has always been commonly thought of as an algae-inducing element and not so much as a helpful nutrient. This is the "old" way of attempting to place blame on the algal woes many folks once had. It's about as true as high light causing algae. P's role in the planted aquarium is an important one, supplying much needed elements in the role of DNA & RNA replication and such things related to growth. P can be made available in the organic and inorganic forms. Some organic forms include fish waste, food, decaying plant matter, bacterial processes, etc. Inorganic forms would include fertilizers such as KH2PO4.

When given other necessities that promote plant growth such as light, CO2, and other nutrients, Phosphorous can limit growth when not in adequate supply. Unlike Nitrogen deficiencies, P deficiency will not bring growth to a screeching halt, but it will hinder growth and a plants ability to uptake other nutrients. When P limiting conditions exist, the conditions become ripe for algae to take over due the slowed uptake of other nutrients--thus decreasing the plants ability to out compete algae for nutrients. In the case of P limitation, algae growth is typically not as severe as Nitrogen limitation and Phosphorous excess. When N & P are in excess and another nutrient(s) becomes limited, massive algae growth is likely to occur. Fortunately, when P is limited in the well-lit, CO2 injected aquarium, Green Spot Algae is a likely warning sign. It does not mean P is zero, but it does mean P is being limited, and plants are not allowed to partake in the luxury uptake (excess uptake allowing for the storage of nutrients within the plant) of nutrients.

Phosphorous can be a tricky nutrient to understand and to test for. When dealing with a such a small range of quantitative values, and a lack of accurate test kits, it's important that the aquarist gain a substantial feel for Nitrogen in order to understand how Phosphorous complements it. In other words, if you know N is at an adequate level and growth slows, P could be limiting. Visually, plants can display signs of N deficiency by turning colors (red, orange, etc.), as P limitation can have a similar effect, but usually not as profound. In conclusion, I would recommend to know the amount of P in your water as found in your local water report, and then use an appropriate calculator to know for sure how much P you are dosing. While planted tanks may differ in their needs, I would recommend a minimum of 0.5ppm to 2.0ppm. While more can be kept, I would advise against it in the minimalist approach this nutrient guide is taking.

Potassium

Potassium's (K) role in aquatic plants is an important one, but is very different than N & P. While N & P play the role of plant "infrastructure," K's role is one of plant "optimization," as it optimizes photosynthesis. It doesn't really do anything fancy, like replicate DNA/RNA or produce enzymes/proteins, but it helps keep them in a constant state of activity. K can be supplied in part by just about all "preferred" fertilizers such as Flourish, TMG, KNO3, and KH2PO4. One of the best facets of K is that it does not cause algae growth. Another is that there is no real minimum or maximum level that must be held constant--a ballpark figure often works well. The worst is that it cannot be tested for (without having a lab handy). However, as I propose in the article, you wouldn't need to test for it anyhow.

It can be difficult to tell if the addition of K in the planted tank actually does anything. However, a limitation can hinder the use of N & P in the plants. While I discourage blindly dumping K into the aquarium, the use of fertilizer calculators can give you a good ballpark figure so as to prevent limitation and excess. A sure sign of limitation are pinholes in plant leaves. This can most commonly be witnessed in Hygrophila species, such as polysperma and corymbosa varieties. It is suggested that enough K can be dosed by using KNO3 and KH2PO4, and I believe in some cases, it is. When KNO3 & KH2PO4 dosing may be low, either due to excessive fish load, high tap water levels, lower lighting levels, etc., the use of K may be mandated. If in doubt, you might wish to dose K for a certain period of time (maybe 2 weeks) to see if you find a benefit. In conclusion, I would propose that you shoot for a minimum of 10ppm, as estimated by a dosing calculator. While larger values will not hurt, excess K will likely have no effect, is wasteful, and goes against this minimalist approach.


Up next will be carbon! This might justify a second article in itself.

Continue to post #21 for carbon!

[Cutlass]

Holy cow, just what I was looking for . My Wisteria is starting to wilt and I'm thinking I'm not fertilizing enough.

[SoleilReine]

Thank you Avalon! Will someone for the love of Pete make this a sticky?

[Orion]

Many times we agree that the use of carbon is quite useless unless removing med's from a tank, yet in the 'Starting Fresh' section, you say to add carbon after the tanks have been setup. Would you care to elaborate on why you want to add carbon at this point?

[TLH]

That Activated Carbon reference comes in the "Resetting an Existing Tank" section.I think it's valid.

[Shaunna]

No, it is in the setting up of a new tank as well, TLH. I was wondering the same thing, Orion. I then started thinking that since we hadn't started adding ferts yet that per haps is was just to help out with cleaning the water and stuff since everything at this point was new. Essentially just like setting up a nonplanted tank because we aren't adding anyhting and we don't want an accumilation of anything yet. IS that right, Avalon? I am really trying to get this stuff down. I want to use this method with my 29. IT is by far the easiest I have come by. I was wondering though, would my tank still be ok to do this way because essentially it is new to plants but has been set up without plants going on 4 months.

[fishtrap]

Originally Posted by SoleilReine

Thank you Avalon! Will someone for the love of Pete make this a sticky?

Harumph Harumph Harumph!

[TLH]

Originally Posted by Shaunna

No, it is in the setting up of a new tank as well, TLH.

So it is.I must learn to read more thoroughly. Anyway,considering the fact that water parameters all over the place are different it could be good to run carbon for a while if you want to set a baseline of sorts.