03-20-2011, 12:49 PM
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Cabomba caroliniana is in our profiles (thus the name is shaded) so you will find info on this one there.
The Ludwigia peruensis is probably what was originally (1988) incorrectly named L. perennis, the correct scientific name is Ludwigia glandulosa which is a red leaf variety. Kasselmann says this is a difficult plant to keep alive, and even in ideal conditions (intense lighting, nutritious substrate and water, plenty of carbonic acid in the water, and a temp below 25C/77F) it will grow slowly. In less than optimum conditions it will quickly begin to disintegrate, usually from the bottom up. [See also comment below.]
Ludwigia arcuata [not arcuta] needs intense lighting to remain red; with less intense light it will be green.
Iron is often suggested for red leaf plants, but this is only one small requirement. As I mentioned above, these plants need more intense light than green leaf plants (generally speaking) and a nutritious substrate and water column. I came across one comment from a planted tank aquarist that an Eco-complete substrate plus fertilizer tabs next to this plant's stems was needed and even then the lower leaves regularly came off. He also mentioned mega-light.
Iron is a heavy metal which is highly toxic to all life forms in sufficient levels, so it must be balanced with all other nutrients and light (plus CO2) so that the plants can use it. If any nutrient is in excess to what the plants can assimilate, they can take up some as a toxin but this is limited and the rest remains in the system where it will harm both fish and plants. For these reasons I always recommend a balanced fertilizing approach, one that contains all nutrients.
Last edited by Byron; 03-20-2011 at 12:52 PM..