A guide to fertilizing your planted aquarium

[malkore]

This post assumes a medium to high light tank. Low light tanks need very little fertilization, which I do bring up at the end of the post.

Fertilizing your planted tank goes hand in hand with adequate lighting, and CO2 injection. Think of these as the holy trinity to a successful planted aquarium.
The amount of light you have will dictate to some degree how often you need to add fertilizers. The types of plants also have an impact on dosing routines - a tank full of fast growing hygrophilia will use more ferts than a tank of anubias bartari, even under the same lighting conditions.

There are macro-nutrients, and micro-nutrients. Macro's are Nitrogen, Postassium, and Phosphorus (carbon from CO2 is also a main nutrient, but we won't call CO2 a 'fertilizer' in this article). Think of these as carbs, protien and fat respectively, while CO2 is basically the 'air' plants breathe.

Nitrogen (or nitrate) gets used on a daily basis, and needs to stay at a sufficient level of 5-20ppm, depending on your plants. Most go for 10-20ppm but many red plants don't turn red until nitrates are limited. Nitrate may need to be dosed every day, or at least every other day. I personally shoot for about 15ppm.
I suggest Potassium Nitrate (KNO3) for dosing. 1lb should last you a while.

Potassium levels can be kept around 10-20ppm. There's not a potassium test kit out there that can be trusted (unless you drop $45 on a LaMotte kit), so just add enough to put 15ppm in after a water change. Then dose another 5-10ppm mid-week and you should be ok. Overdosing potassium doesnt' cause algae, and unless you have wickedly soft water it won't affect calcium uptake either (the only real con to overdosed potassium). If you find you have to dose a lot of nitrate, and you use potassium nitrate for dosing, you shouldn't need the second dose of straight potassium mid-week.
I suggest Potassium Chloride (KCl) or Potassium Sulfate (K2SO4). Start with 1lb, but potassium is what I go through the quickest.
*edit* Some recent research from Tom Barr has shown that you really cannot overdose potassium. People dosed for a few months at 100ppm potassium, and no plants showed calcium deficiencies. Dose all the K you want, but there's no real need to exceed 15ppm per dose.

Phosphates are needed in low levels (just like fats). Keep your phosphate levels in the .5 to 1.5ppm range to avoid algae, but keep plants thriving. SeaChem makes the best phosphate test kit, hands down (well, Lamotte's is nice, but who wants to spend $60 on a test kit when a $10 kit works just as well?) Phosphates can be dosed up to 2-3 times a week, and as you become more comfortable with dosing and knowing what's going on in the tank, you may want to bump up to 2ppm of phosphate, especially if you get a lot of spot algae on the glass.
Mono-potassium phosphate (KPO4) or Fleet enema (from a pharmacy) are good for dosing phosphate. A little goes a long way...you'll make a dosing solution of this, so I'd start with a half pound.


Now, as far as trace nutrients go, I personally use Plantex CSM+B as a trace, adding it 2-3 times a week. SeaChem Flourish also makes a good trace dose in high-light tanks. Don't waste money on Flourish Trace...it's nothing more than very hard spring water, so unless you have softened water, Trace isn't worthwhile.
Iron is probably the most important trace, but don't over do it. No iron test kit is worthwhile here, as none of them will accurately read a low level of 0.1-0.3ppm which is what you're after. A lot of people just add a few drops of chelated iron every few days to maintain this low level. www.gregwatson.com also carries Plantex CSM+B plus Iron...with a higher iron level than normal Plantex. I've heard good things about it but haven't tried it yet myself. 1lb of Plantex will last you a LONG time.

Low light tanks

In a low light tank, you really only need to worry about potassium and iron. Leaf Zone is a potassium & iron only liquid fert, and I've used it with some success. Low light tanks don't rip through nitrate or phosphorous that quickly so the fish bio load should be enough. SeaChem Flourish is a good low light fert, as is Plantex. Tropica Master Grow should be fine too.

Where to get ferts

I strongly recommend www.gregwatson.com for ferts, as he sells all the dry forms of the ferts you'll need, and he's doing this to help hobbiests, not make a lot of cash, so his prices are going to be very reasonable.

If dry, greenhouse grade ferts are intimidating, or you have a low-light tank, or just no way to order online, try SeaChem's Flourish line of ferts.

How much to add

Chuck's aquarium pages are what I use for determining how much fertilizer to add to achieve a desired ppm level.
http://www.csd.net/~cgadd/aqua/art_p...osage_calc.htm

There's a downloadable version of his calculator here: http://www.csd.net/~cgadd/aqua/art_plant_aquacalc.htm


If you use a brand name like SeaChem, Kent, or TMG - try using this site to determine how much fertilizer you need to add: http://www.leon-huang.com/doser/



(This thread is for information and resources only. Post questions in new threads. -- czcz, 9/06)

[czcz]

Excellent calculation/formula site from mass percentage, for some things not covered by Chuck Gadd's excellent calculator: http://users.ev1.net/~spituch/Chemicals/chemicals.html

Mass percentage calculator: http://chemmac1.usc.edu/bruno/java/compo.html

KH and pH calculator: http://dataguru.org/misc/aquarium/calKH.asp

Plantex CSM+B calculator, TMG, and general/commercial solution calculators: http://justanothertank.com/calcs.php

(ediited to merge subsequent posts)

[czcz]

The Estimative Index of Dosing, or No Need for Test Kits (EI)
EI light: for those less techy folks

Zezmo's EI - Dose Routine is also an excellent nutrient calculator/spreadsheet: http://webpages.charter.net/zezmo/EI..._v4_public.xls
Accompanying thread.

(edited to update Zezmo's spreadsheet to the newest version and link his thread.)

(edited to correct EI links. Thanks rkilling1.)

[czcz]

How to dose Fleet Enema for PO4: http://www.aquariumadvice.com/viewtopic.php?t=80770