Hornwort - angel or demon?

Marc Jackson

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16 Mar 2019
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Suffolk - almost
It's in my shopping basket along with Water Wisteria to help balance things out in a new set-up, but what is the downside of growing it?
 

three-fingers

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15 Sep 2008
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Scotland
It grows very fast and blocks out the light, and doesn't have real roots so it is often a bit awkward to position.

Other than that, it's amazing! As a fully aquatic plant (submerged growth only) it fights algae very effectively compared to most of the amphibious plants we grow in aquariums, competing for nutrients with it's fast growth and directly inhibiting algal growth with allelopathy. Like many fully aquatic plants, it can utilise carbonates as a carbon source, giving it a huge advantage over other fully submerged plants in non-CO2 injected aquariums with harder water.

So a brilliant plant to keep new set-ups stable and inhibit algae growth, but not so ideal for a high-light CO2 injected set up if you want the focus to be on other plants.
 

Oldguy

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27 Aug 2018
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Gloucestershire, UK
downside of growing it?
Hornwort may fall apart if grown under high light and in soft water.

It can be grown floating or vertically if a few stems are snagged in say a ceramic ring. The lower sections will die but you can just keep replanting.

In ponds it can form dense stands of growth, the lower sections of stem just lodged in the mud and the shear mass of the growth will keep it vertical.

If there is room for a patio pond ie a tub or just a big bucket keep some growing outside as a reserve source for aquarium planting.

Interesting point. Do you know if some aquatic plants have this effect on other aquatic plants.
 

three-fingers

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Scotland
Hornwort may fall apart if grown under high light and in soft water.
Very true, this happens in my tanks with higher light intensity, it grows super fast but is very brittle.

Interesting point. Do you know if some aquatic plants have this effect on other aquatic plants.
Yep! Here's an interesting article: https://pdfs.semanticscholar.org/3fbe/c50175c1f35e867b5039cdd362b552e1e4ea.pdf

I think there were some good examples in Diana Walstad's Ecology of the Planted Aquarium too, I'm at work at the moment so will check the book when I get home :).
 

Oldguy

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27 Aug 2018
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Gloucestershire, UK
interesting article
Very interesting read. It happens with terrestrial plants, but is difficult to truly isolate as a causative agent. Older books on aquatic plants often state which plants are compatible and those which are not. However may be growing conditions are the major factor. A real eye opener to find that even in a small glass box nutrient levels can vary in the water column around one plant compared to the next.
 
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