potassium deficiency or snail nomnoms? - Page 2 - Tropical Fish Keeping - Aquarium fish care and resources
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post #11 of 12 Old 01-12-2011, 06:57 PM
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But at some point, lets say, the tank is lacking in iron, but has an excess of potassium. Adding a comprehensive fert like Flourish would add both iron and potassium to the tank. The plants, needing iron would utilize it right away along with the ratio of potassium that it can use, but at some point wouldnt the plants stop being able to use or take up excess potassium due to not enough iron in the water to help it and the mineral would just build up in the water until a water change is done wouldnt it? <-- I dont know if im articulating my question correctly.

I thought plants would need to absorb a certain ratio of minerals and nutrients? IE if theres a certain amount of mineral A then only a certain amount of mineral B will be used. The plant cannot just utilize everything in the water right?
Correct on the last question. In the presence of sufficient intensity light, plants need a specific ratio of 17 nutrients. As soon as one of those is no longer available, photosynthesis cannot continue and the plant stops growing. Now, understand that some nutrients are probably less crucial than others, so a depletion of nickel for instance may not cause the plants to shut down. This is obviously the reasoning behind the dosing of certain nutrients and not others. We must talk in general terms. But there is no doubt that each nutrient has its function, and needs to be available.

The ratio of nutrients is quite important. Some nutrients in excess can result in the plants shutting down assimilation of another, resulting in a deficiency even though that other nutrient may be available. Your example of potassium and iron is interesting; an excess of potassium cause plants to cease assimilating iron, and iron deficiency results, and adding more iron does nothing, the plants cannot use it because of the potassium excess. I had a similar experience with magnesium; in excess it too caused an iron deficiency that took me months to remedy.

So this means that event hough mineral B (still referencing my example) is in excess, the plants will "take it up," but just wont utilize it immediately?
No. When plants "take up" metals they detoxify them, they do not store them for assimilation. When they assimilate excess nutrients they are storing them for later--though I gather not all plants do this the same. But taking up toxic metals is the plant's way of removing them from the water so they are no longer toxic, just as the water conditioner does; it does not leave them somewhere for later.

I understand that testing for everything is expensive and excessive in most cases, but im just wondeirng if its good for the long run?
I don't see why this is necessary. Aquarists have had successful planted tanks for more than a century without any test kits, and my tanks have been around for more than 15 years with, so far as I know, no issues in this regard. Now, if one is aware that some specific mineral is present in considerable quantity, it may be necessary to do something to negate/remove it. But I suspect this situation is highly unlikely today, unless one is adding excess deliberately.

Byron Hosking, BMus, MA
Vancouver, BC, Canada

The aquarist is one who must learn the ways of the biologist, the chemist, and the veterinarian. [unknown source]

Something we all need to remember: The fish you've acquired was quite happy not being owned by you, minding its own business. If you’re going to take it under your wing then you’re responsible for it. Every aspect of its life is under your control, from water quality and temperature to swimming space. [Nathan Hill in PFK]
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post #12 of 12 Old 01-12-2011, 07:11 PM
Thanks Byron. This has helped me understand how my plants work, im reading Ms. Walstad currently but im not even halfway through yet, although she does a great job explaining things, some of it is still really technical and difficult to understand.
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