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Discussion Starter · #1 ·
I went to my LFS today and got some fertilizer supplements. One of the things I picked up was Flourish Iron. (They only have Seachem ferts in any variety...) I also purchased a Red Sea Iron Test kit. I tested my water and found that there is less iron in my water than the test will register. (Less than .25 ppm) I have a few questions.

1) What should my iron levels in my planted tank be?
2) Will dosing iron have a potentially negative effect on my plants, or is this like my phosphate question where even if I add too much it could not hurt?
3) What are signs in plants that show whether or not I have an iron deficiency? What about an iron surplus?
4) I looked here and could not find a way to calibrate an iron test. Is there a method posted anywhere here on TPT? If not, does anyone know of a way to calibrate this test or to at least check it for accuracy using some known concentration of iron?

Thanks to all for your help!
 

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How Much Iron

Good morning wet...

Fertilizing plants isn't complicated. Plants need two types of ferts: Macro and Micro. The plants get the macros from large and frequent water changes and from your fish, so feed the fish a balanced diet.

The micros come from a commercial source, either dry or liquid. You can research those sources online. I like hydroponics liquids, but do your research.

Testing your water isn't necessary and to me is a waste of money. I would get the micros in the water and don't worry about testing.

B
 

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Iron levels should be 0.1 to 1.0 ppm. If I had to recommend a specific ppm, I'd say 0.2, but I just go by plant condition.

Iron has a fairly low toxic threshold compared to most other nutrients, and you can definitely add too much. But the acceptable range still gives you a tenfold margin of error, so toxicity is fairly rare. See the black streaked anubias and discussion on page 2 of this thread for a possible example.

If iron is too low, entire plants will lose their normal rich colorations and become pale and yellow. Here's a diagnostic chart which includes all major nutrients, including iron:



As for calibrating any test kit, it's just a matter of adding a measured amount of nutrient to a measured amount of distilled water, to produce a known concentration; and then testing to see if the result matches what you expected. The Fertilator will allow you to calculate the result of any given amount of Flourish Iron and water, but if your test kit's lower limit is really 0.25ppm, then it might not be particularly useful. Plus iron tests are reputed to be highly inaccurate, probably because iron can exist in significantly different forms (EDTA/DPTA chelated, non-chelated, gluconates, etc.)
 

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Discussion Starter · #4 ·
Iron levels should be 0.1 to 1.0 ppm. If I had to recommend a specific ppm, I'd say 0.2, but I just go by plant condition.

Iron has a fairly low toxic threshold compared to most other nutrients, and you can definitely add too much. But the acceptable range still gives you a tenfold margin of error, so toxicity is fairly rare. See the black streaked anubias and discussion on page 2 of this thread for a possible example.

If iron is too low, entire plants will lose their normal rich colorations and become pale and yellow. Here's a diagnostic chart which includes all major nutrients, including iron:



As for calibrating any test kit, it's just a matter of adding a measured amount of nutrient to a measured amount of distilled water, to produce a known concentration; and then testing to see if the result matches what you expected. The Fertilator will allow you to calculate the result of any given amount of Flourish Iron and water, but if your test kit's lower limit is really 0.25ppm, then it might not be particularly useful. Plus iron tests are reputed to be highly inaccurate, probably because iron can exist in significantly different forms (EDTA/DPTA chelated, non-chelated, gluconates, etc.)
Thanks DarkCobra! Your explanation and the chart you posted are exactly the sort of thing I needed. In fact, now I will not have to post a few of the other questions I had because the chart has already answered them. I took another look at the range of my Red Sea iron test, and I think I may have gotten it confused with the API copper test. The range goes from 0 to 1.0 ppm, with .1, .2, and .5 used as references. Also, I did not know that the Fertilator would let me figure out how to calibrate my tests. That thing is a pretty useful tool. I am sure that I am overthinking all of this, but once I understand better how everything fits together, then I can stop worrying about it. I always have to know the how and why of things. Thanks again for all of your help, both with this question and the others you have helped me with. I really appreciate the info, and it keeps me from making too many mistakes, which my fish, shrimps and plants really appreciate too.
 
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