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Fertilizing a planted tank may seem unnatural for those of us who have kept "fish only" tanks. To keep lush plants in a fish tank it is almost a neccesity.
To get the kind of growth that you see in the photo section of this board and others like it, you'll need a minimum of 2.5 watts of flourescent light per gallon of aquarium water volume (or 2.5 )WPG. This info does not apply to low light tanks with no co2 injection and adding these fertilizers to a low light tank would be just about pointless.
This post is written in an attempt to take the mystery out of fertilizing your planted tank.

The first requirement is light on the order of 2.5+ WPG.

The second requirement is CO2 supplementation.

The third requirement is macro and micro nutrient supplementation.

We'll assume the lighting requirement has been met.
Co2 supplementation can be accomplished via a DIY yeast and sugar fermenting process or thru the use of pressurised CO2. CO2 levels of 15-30 parts per million(ppm) are the goal.
Most tanks that have the amount of light and co2 listed above quickly get depleted of nitrates, phosphates,pottasium and micro nutrients.

Most of the information regarding fertilizing evolved from the PMDD formula, They advocated mixing all the ingredients together and dosing that. It's a starting point but rather unscientific since each tank and local water parameters differ tremendously. I don't reccomend that you use that method for very long or not at all. It is better to dose all your ingredients seperately according to the needs of your tank.

Nitrates can be supplied via potassium nitrate (KNO3). The target range for nitrates 5-10 ppm.
Phosphates can be supplied via monopotassium phosphate or Fleet Enema. The target range for phosphate is .5-1 ppm or approx. 1/10th nitrate levels.
Potassium can be added via potassium sulfate (K2SO4) or potassium chloride(No-Salt). The target range for pottasium is 20 ppm. Pottasiumm is difficult to test for and is not toxic to fish even at much higher dosages, so it is generally dosed at water change time to a sufficient level to bring the water change volume to that level.
Micros can be added via a trace mix supplement such as Plantex CSM or Flourish or one of the other Aquatic plant supplements. Some of the original info regarding micros is very vague and most people dose micros increasingly till dosing more produces no significant improvement. It can take weeks or months to determine what that level is for your tank. Patience is the name of the game there.

The best place to get the macro chemicals is,, click "shop online", next page click "plant nutrients", on menu click "chemicals".
Micros can be purchased at your LFS or online fish stores under the plant supplements. Flourish, Flourish Iron, Kent etc. Most of the prepared solutions don't contain enough iron. Eco Enterprises sells a "fish trace mix" that can be used to dose your tank for micros, It is not listed on thier site but they have it and it can be purchased over the phone. Make sure you ask for "fish trace" or they'll send you a trace supplement for terrestrial plants.
Here's another link which carries everything needed to fertilize your tank . Nice link, thanks to Rex Grigg.

After you bought all this stuff, you'll need to know how much to add to your tank to bring it up to the levels specified above. "Chucks Planted Pages" has a unique calculator for that heres the URL for that;

You're going to need a nitrate and phosphate test kit, at least in the beginning, to determine what your tank levels are and to make sure that your dosing regimen is correct. Failure to so will probably result in "Algae soup". After a while the kits will probably be used only occasionally once you get a feel for your plants.

Water changes on the order of 30-50% weekly should be done when fertilizing to reset the tank and prevent buildups of one nutrient or the other.

I hope I covered it all, but I'm sure I left something out. If anyone has any input just post it here and I'll try to work it in. :)



By popular demand, here's a basic outline of what the specific fertilizer elements do for your plants. This outline is based on terrestrial plants but the concepts are the same.:

There are six primary nutrients that plants require. Plants get the first three -- carbon, hydrogen and oxygen -- from air and water. The other three are nitrogen, phosphorus and potassium.

Nitrogen helps plants make the proteins they need to produce new tissues. In nature, nitrogen is often in short supply so plants have evolved to take up as much nitrogen as possible, even if it means not taking up other necessary elements. If too much nitrogen is available, the plant may grow abundant foliage but not produce fruit or flowers. Growth may actually be stunted because the plant isn't absorbing enough of the other elements it needs.

Phosphorous stimulates root growth, helps the plant set buds and flowers, improves vitality and increases seed size. It does this by helping transfer energy from one part of the plant to another. To absorb phosphorous, most plants require a soil pH of 6.5 to 6.8. Organic matter and the activity of soil organisms also increase the availability of phosphorus.

Potassium improves overall vigor of the plant. It helps the plants make carbohydrates and provides disease resistance. It also helps regulate metabolic activities.

There are three additional nutrients that plants need, but in a smaller amounts:

Calcium is used by plants in cell membranes, at their growing points and to neutralize toxic materials. In addition, calcium improves soil structure and helps bind organic and inorganic particles together.

Magnesium is the only metallic component of chlorophyll. Without it, plants can’t process sunlight.

Sulfur is a component of many proteins.

Finally, there are 8 elements that plants need in tiny amounts. These are called micronutrients and include boron, copper and iron. Healthy soil that is high in organic matter usually contains adequate amounts of each of these micronutrients.
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