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Discussion Starter · #1 ·
Honestly Im not sure where to start. I feel a little overwhellmed with the fertilizing thing. Ok I've got the lights, and the compressed CO2 with the probe. Basically I have been reading and reading everyone is talking about the individual nutrient and it is just confusing me. I bought some Florish, Florish Iron, and Florish Tabs. It seems no matter how much Florish Iron I add I still don't test in the acceptable ranges. I am going to buy a Liquidoser becuase I would really like to automate the process as much as possible.

40 Gallon Tank
AHS 4x36 watts (3.6wpg)
Compressed CO2 with a milwakee probe
Weekly water changes (50%-60% or so)

My ideal situation would be to learn what should be dosed daily that way I can just automate the whole thing. I realize that it will take some fine tunning but I need a ballpark figure here. My plants don't look that hot to me. Most of them have a brown edge, some have a dark green algee on them. Any help or link would be appreciated. ](*,)

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215 Posts
After you read all the differnt approaches you may find that some people seem to speak to you more than others. Pick one guru read all they have posted, ask questions if they seem unclear and then follow that persons plan as best you can. Often ppl read through all these posts, pick and choose a a bit of this, a bit of that, and end up with some peculiar notions. After you try one persons methods you will be in a better position to evaluate other methods.

The estimative index is one popular method that doesn't require testing; though many who practice it often get very caught up in testing. It is not a bad starting point. Tom Barr, here posting under the avatar "plantbrain", can provide a link to his version of the estimative index.

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4,116 Posts

Don't focus too much on small details and be patient about the tank development. To get better advice please use the "I Need Help Template" that will give the other members better idea of your tank - see it here. Here is my take on your tank:

I assume you maintain proper temperature and have good circulation so I'll talk about the nutrients. You have a lot of light so you really have to make sure your plants never run out of nutrients.

First make sure that your CO2 concentration is right. A good number as you probably know is 20-30 ppm. Use the pH/KH table for that calculation but verify your readings for KH and pH because often the probes and test kits give incorrect readings.

Same goes of N and P - make sure you have N= 5 to 10, and P= 0.25 to 1. Verify your test kits...

The iron concentration: Testing the iron in the tank water can be misleading and frustrating because once added to the tank the iron quickly turns into an unreadable form or gets used up. A good approach is to add iron every day as oposed to once or twice a week. How much to add every day? Perform this simple test:

- Take a one gallon jug of distilled water (from any grocery store)
- Add 1 ml. of Fluorish Iron to the jug and shake well
- Use your iron test kit to check how much iron you have in the jug as a result of adding 1 ml. of Fluorish Iron
- If needed add more Fluorish Iron untill you get a reading of 0.1 ppm.

At the end of that test you will know how much Fluorish Iron you have to add to 1 gal. of water to get the iron concentration to be 0.1 ppm.

Multiply that amount of Fluorish Iron to the volume of your tank (40) and add that amount to the tank every day. Keep in mind that the other product that you have (Fluorish) contains iron too so you will be adding about 1/3 extra iron with the Fluorish.

Verify your iron test kit too. :D

You will have to use Fluorish and Fluorish Iron together because Fluorish adds much needed trace elements. I can't tell you how much Fluorish to add - you need to figure that out by watching your plants. At first add what the label says but break it into daily doses. If your CO2, N, P, Fe are in line but your plants are not doing great you need to carefully increase the amount of traces (=Fluorish) that you use. If you see algae appearing that means that you are adding too much traces and the reason your plants are not doing well is something else.

I'd say forget the Fluorish tabs for now.

Lastly a positive change will not happen in the matter of a few days. If you indeed keep the nutrients in a good range you should have a much cleaner and healthier tank in about 3-4 weeks. That of course is a very general statement. Just be consistent and remember that the tank will go through phases and will eventually become healthy.


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473 Posts
For the sake of simplicity, there are only 3 things to remember: Macronutrients, Secondary Nutrients, and Micronutrients.

MACRONUTRIENTS are elements required by plants in relatively large amounts. These include Carbon (C), Nitrogen (N), Potassium (K), and Phosphorus (P). C is provided through CO2 (Carbon Dioxide). N is provided through KNO3 (Potassium Nitrate). P is provided through KH2PO4 (Potassium Monobasic Phosphate). By dosing KNO3 & KH2PO4, no supplemental K is required.

SECONDARY NUTRIENTS are elements required by plants in larger quantities than the micronutrients and in lesser quantities than the macronutrients. These include Calcium (Ca), Magnesium (Mg), and Sulfur (S). S is usually available in large amounts in our tap water as well as via other fertilizers so it is not often discussed. Ca & Mg are provided through the GH. As long as the GH is 3 degrees or higher, then you don't have to worry about these two nutrients. If not, then they have to be supplemented through CaMg(CO3)2 (Dolomite/Limestone).

MICRONUTRIENTS are elements required by plants in very small amounts. Most notable is Iron (Fe). All other micronutrients are not often referenced because we assume that as long as the Fe needs are met, the other micronutrients will be as well since many micronutrients mixes are quite comprehensive in composition.

Therefore, there are, at most, 4 things you have to add: CaMg(CO3)2, KNO3, KH2PO4, and a micronutrients mix; all of which can be conveniently purchased inexpensively through Greg Watson.


Given your size tank, it would be IMHO less cumbersome if you dose all these chemicals dry instead of making a "magic solution" as there are associated complications that shall be addressed should you opt for the Eheim Liquidoser. :wink: In either cases, you should FOREMOST obtain a comprehensive water report from your local water company so that you would know the baseline levels for the macro/secondary/micronutrients.

I'll reserve the specifics on dosage amounts to others. :mrgreen: I hope that the above information would help familiarize you with some of the terms hobbyists often throw about.
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