# Wierd deposite on my plants



## valerie27 (Feb 13, 2008)

hey, i have a wierd deposit on my leafs, it looks like dust ???? what is that and what can i do, unfortunatly i can not add any algea eaters because my jewel fish eat them.....


----------



## wtac (Mar 17, 2006)

What you are seeing is called "biogenic decalcification". Totally normal if your source water is high in mineral content (GH and kH). 

HTH


----------



## Chris S (Dec 19, 2007)

Wilson,

I was under the understanding that biogenic decalcification only took place in typically low co2 tanks and is a process used by some plants to extract co2 from calcium.

I had some crypts that I believe did the same thing.

Please let me know if I am wrong...I hate being wrong


----------



## dekstr (Oct 23, 2007)

Interesting.

Stripping Co2 from calcium?

So you meant something like calcium carbonate?

I always thought this happened more often in SW as they have much higher calcium concentrations (minus saltwater plant part). Don't know what I'm talking about now. ;P

INTERESTING!!!


----------



## wtac (Mar 17, 2006)

In conditions where there is not enough CO2 added to the system required by the plant density, low flow and the water is high in calcium as well as a moderate kH, the process of CO2 uptake via HCO3 will create an area of high pH around the leaf. Calcium carbonate particles will form (calcium carbonate precipitate) as it's solubility is very low at high pH. Due to the low flow, the particles settle on the leaf looking like dust instead of going into the water column.

Hope I explained that correctly...mind is mush from late nights and early mornings...LOL!


----------



## Chris S (Dec 19, 2007)

I'm still not sure if we are talking about the same thing.

From my understanding biogenic decalcification is an active process used by "some" plants to gain carbon from water. It is done by extracting the carbonate component from calcium carbonate (ie. there has to be a source of calcium in the water column already).

Are we still talking about the same thing Wilson?


----------



## Brian (Mar 14, 2006)

I think you are both speaking of the thing. There is always calcium in our tap water which is why when your tank evaporates, it leaves all the calcium buildup on the sides of the tank but I assume you already know this


----------



## valerie27 (Feb 13, 2008)

the wierd deposit was due to a really dirty filter lol (oupss)


----------



## Brian (Mar 14, 2006)

ROFL!! All this talk about biogenic decalcification and the problem was just a dirty filter... life.


----------



## wtac (Mar 17, 2006)

Valerie, you are killing Chris and I here...LOL!

I think we are looking at different perspectives. From what is described in hobbiest literature is partially correct, IMHO. In theory, to extract a carbon source from calcium carbonate, first the solid must be converted to an ionic form, which is not the case with respect to the manner in which we set-up our aquariums. 

Looking strictly at the point of view of the body of water, there is no "solid" calcium carbonate thus the notion is an invalid point of view. What there is to "work with" is ionic calcium and bicarbonate that freely floats around in solution. It's the activity of the plant wanting that carbon source from the bicarbonate which creates the conditions, in conjuntion of low water movement, for calcium carbonate to from and fall out of solution.

To further expand; in tap water, especially in the GTA, there are dissolved calcium ions and bicarbonate ions where they are in solution and overall the water is clear. The environmental factors that biogenic decalcification will occur is at the leaf of the plant, low flow where the bicarbonate uptake where CO2 is "extracted" creating a localized are of a high pH (~pH=10). In this localized area, it is an ideal environment where the interaction of calcium ions and bicarbonate ions to "preferably" combine and eventually create the solid that settles on the leaf.

I think we are splitting hairs here...LOL!


----------



## Chris S (Dec 19, 2007)

Hey Wilson,

I think I understand now what you are saying, and essentially we are in agreement. I didn't mean to doubt you at all, I'm just not as sure of the actual process that takes place, which it seems you are!

Excellent post though, it explains the process to less informed people like myself


----------



## valerie27 (Feb 13, 2008)

LOL im so sorry, but at lease now theres a post on the other reasons why it could happen LOL


----------



## wtac (Mar 17, 2006)

I've always had a difficult time writing and conveying information to a broad audience. Honestly, _*I humbly thank you all*_ for helping me to improve getting my nerdy thoughts out in a manner that is understandable and "tweak the geek" in those that care to read my rambles...LOL!


----------



## jrs (Mar 18, 2006)

wtac said:


> Valerie, you are killing Chris and I here...LOL!


 That is a good explanation. Interesting


----------

