tannins, apparent effect on floating plants

[Ben Rhau]

Hi all,

I seem to notice a correlation between the darkness of the tint in my tank water and the appearance of pale, small, or dying leaves in my Salvinia natans (surface floater). No intended difference in light output at the top, and same water source. In my most recent case, I have some new driftwood I moved from one tank to another. It releases a lot of tannins, and I see the floaters doing worse as the water gets darker. I've observed it in my quarantine tanks, too, when I've added alder cones and catappa leaves. I've added liquid ferts, and it doesn't seem to help.

Has anyone else observed this? Is this a known phenomenon, and what do we think is the mechanism?

Thanks,
Ben

 

[MacZ]

That's somewhat counterintuitive. Humic substances tend to chelate certain micronutrient ions, thus pushing their bioavailability.

pale, small, or dying leaves in my Salvinia natans (surface floater)

Those are signs of nitrogen-deficiancy. I haven't heard of any correlation between humic substances and nitrogen compounds.

 

[Ben Rhau]

I don't understand it either. The two tanks where this is currently happening are the two most heavily stocked with fish. The same plants are thriving in shrimp tanks that have very little nitrogen. Also, dosing with ferts hasn't helped.

Those are signs of nitrogen-deficiancy. I haven't heard of any correlation between humic substances and nitrogen compounds.

I would have assumed the correlation was the other way (improved N uptake).

 

[MacZ]

I would have assumed the correlation was the other way (improved N uptake).

If any, yes, exactly this.

 

[Mazan]

That is strange. I have not noticed anything like that with water lettuce, I usually only see yellow or dying leaves when there are too many floating plants in a tank, and have assumed that is because of too much competition for nitrogen.

 

[Apistomaster]

I also have trouble growing plants in my black water Betta coccina tanks. Have not tried Salvinia natans but couldn't get a starter culture of Salvinia minima to take off. Najas sprigs barely hang on. Potted Crypt. wendtii does fine as does Anubias barteri super glued to the bogwood. Hair algae sometimes takes off if I leave the lights on too long.
I have a thriving garden of two species of Sundews, Drosera spatularia and Drosera nidiformis planted in a Gladware sandwich container filled with Sphagnum moss in my Betta tanks on a plastic frame platform. They are in a "double boiler" type of setup so top container freely drains into the bottom container. They aren't in contact with the aquarium water. I only keep the aquarium half filled. I'm using RO water and Cattapa leaves and the fish water is dark.

 

[Ben Rhau]

I see obvious nutrient deficiencies in some tanks and not others. As I observe more, I don't think it's related to tint. But I do have tanks with nearly identical water chemistry and see plants happy in one and not the other. These are all soft water tanks.

 

[xSparkleZ]

Posting to follow the thread as I also have the same problem with my frogbit.

 

[dw1305]

Hi all,

But I do have tanks with nearly identical water chemistry and see plants happy in one and not the other. These are all soft water tanks.

I'd just start adding a trickle more nutrients, if things don't improve you will know you have issues with <"Liebig's limiting nutrient">, you just don't which nutrient it is.

as I also have the same problem with my frogbit.

Have a look at <"https://www.ukaps.org/forum/threads/what-is-the-“duckweed-index”-all-about.73647/#post-742177">. If you have time I'd read the whole thread.

cheers Darrel

 

[anewbie]

This is a combination of red root floater and frog bit; so different species but i add no fertilizer (other than fish food and leaves) and ec is around 25:

The density has double the past 2 or 3 weeks (density of plants) so they seem fairly happy though i suppose the ones in tap water grow faster.