Do I need potassium and iron? - The Planted Tank Forum
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post #1 of 4 (permalink) Old 09-19-2014, 05:15 PM Thread Starter
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Do I need potassium and iron?

Hi, I am new to planted tanks. I have cobomba, red ludwigia, java fern, moneywort and pennywort. My tank is 29 gallons and I use an aquaticlife t5 fixture that is 48 watts. I guess this makes it low light? Anyway I have been adding flourish comp. and excel and everything is starting to grow and look really healthy. ( I am a little worried about my bolivian ram as it seems he does not like when I add excel). So since I don't what to add anything else to the tank that isn't needed do you think my tank would benefit from iron and potassium?
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post #2 of 4 (permalink) Old 09-19-2014, 06:07 PM
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You have a 2-bulb T5HO fixture with good reflectors on an 18" high tank... You are probably not low light.

In general, do not use watts/gallon guidelines on modern light fixtures. It has no correction for the higher efficiency of modern lighting.

If it is just sitting directly above your tank you are probably above PAR/PPFD of 50. (lower end of high light). If you have it raised well above the tank (20" above the tank rim or so) you might be in low-light territory.

See the graphs for the 4-bulb version of this lamp, having PAR/PPFD of about 115 at 20" height. You should be somewhere near half that (57.5-ish)

if your inhabitants don't like it, try reducing the dosage and watch for algae problems.

Fertilizers in general:
You've got good growth and no signs of deficiency, so you are probably OK for now. Keep an eye on the tank and see if things change later.

Your Flourish Comp has a decent amount of Iron in it. Not a ton but it is a decent amount, so you probably aren't severely low. The red ludwigia might get more red with a bit more iron, but you should probably figure out the amount of iron you're already adding.

Unless you're adding some elsewhere, you might need some. Flourish comp also contains *some* potassium, but compared to plant needs the amount is relatively trivial. Fish waste also adds some, but it too is relatively low in potassium. Watch for deficiency signs and add if needed.
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post #3 of 4 (permalink) Old 09-19-2014, 07:10 PM Thread Starter
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thank you for that very informative answer. I am dosing excel a little lower than it says on the bottle. My bolivian would'nt eat yesterday but otherwise was acting normal.
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post #4 of 4 (permalink) Old 09-19-2014, 07:14 PM
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Pictures would help for estimating the total plant mass. As the plants grow they will need more ferts. You can't skip any as it will inhibit plant growth.
But as was already said, just watch for deficiencies.
I have a fairly low amount of plants and in a 10g was dosing 2 ml Flourish comp AND
3.5 ml Tetra Pride. Both contain iron and some Potassium. But it wasn't enough so I
had to add more. And since I had some of the dry ferts I now use both till the liquids run out.
On the really works best if used daily. But I don't use the higher doses that
are suggested after a water change and for start up. I used 1 ml per day for 6 months
and then I increased it to 2 ml per day which I don't think is necessary for you.
But my RCS acted strange when I first used it but now they don't react when I use it double.

The shortest distance between any two points is a straight the opposite direction...
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