I like to take an hour every morning before my daughter gets up to read. Today I picked up Walstad's "Ecology..." and read the chapter on plants as water purifiers. This interests me as I see a lot of people on here and other forums talking about metals in tap water from running warm-hot water out of the tap for water changes(increased temps leaching unwanted metals i.e. Pb, Cu and whatever else is in pipes and tap water these days). Walstad talks about the ability of plants to uptake metals at an astonishing rate and capacity. This and the binding of these metals by DOC. Now, in high-tech EI dosed systems I would think the large regular water changes would reduce a lot of the metals present but, at the same time would also remove DOC. In a NPT set-up(Natural Planted Tank, Walstad or, whatever one prefers) where water changes are seldom performed does the presence of DOC and supposing there is very healthy growth in plants, I would presume that again metals would be either bound by DOC or into plants. At the same time any keeper worth their weight is going to be using a water conditioner that removes metals. I guess my question is that is metal toxicity something that we should be concerned with or, really just ANOTHER thing to argue about? Thoughts, questions, comments and clarifications welcomed!

Regards,

HDB

Most water treatments do not remove metals from the water, they generally convert them to a less hazardous form. ie: Seachem prime does this by reducing them (in the sense of the chemistry term for gaining electrons, not lay term for 'making less present'). Reduced metals are generally less reactive, thus less toxic.

That said, yes, plants do uptake many heavy metals.. some of which are micronutrient fertilizers. Take Cu and Zn for example... both heavy metals that are absolutely essential nutrients for plants.

As far as toxicity goes... I think most that are worried are doing so without any real cause... "heavy metals" is a scary term. Unless you've actually measured high levels of a particular heavy metal in your water, you're probably adding more in your fish food than your tap water (hot or cold) contains... At least IMHO.

That's kind of what I was getting at. Is ME-TAL TOX-I-C-I-TYYYYYYY(scariest voice your mind can create) really "worth" what people make it out to be? Me.. I don't worry about the hot v cold tap water. Me.. I like to run it warm for my betta and if it gets too "hot" cut on the cold water! Me.. I'm not worried.. the plants will take care of it. I'm just asking so other people can realize that it's not that big of a deal.

It *might* be a deal for folks using well water and not dosing a dechlorinator with water changes... maybe, but you might be better off buying a lottery ticket....

However, since most of us using city-water have chlorine, dechlorinators are necessary. Nearly all dechlorinator products have metal detoxifiers in them.

For those using dechlorinators, the risks are basically zero, even if you have some heavy metals in your water and no plants or dissolved organics, the dechlorinator will likely take care of it.

Metals dissolve very, very slowly into water, unless the water is acidic (for some metals). So, the only time you might get copper or lead in your water is when you have no water flow for a long time, then, without flushing out the piping first, you add tap water to your tank in large amounts. Water heaters use linings that protect the metal containers from the water. But, almost all houses use copper plumbing, most with lead based solder holding the connections together. So, in theory at least, if the water sits in that plumbing long enough it might dissolve some of those metals into the water. But, if you flush the plumbing for a few minutes before using the tap water in the tank, you should never have that problem.

Okay, so, dechlorinators containing EDTA and the presence DOC aside... is there any real reason to worry about heavy metals in any tank with healthy plant growth? For example Cu, based medication? I've seen talk about it being "harmful" or, "harsh" to plants, fish and, inverts. Is the Cu "bonded" in a way that makes it unobtainable to plants but still harmful to plant and fauna? Or, will plants be able to use or, uptake this form of Cu to bring the concentration to "less harmful" levels?