This plant is slow growing for stem plant, hence, some leaves are prone to green spot algae. I've grown it well with 2 to 4 watts gallon in soft water. Without CO2 and EI, the leaves are smaller and grow is slowed considerably. In spite of the slow growth, this is a welcome trait by keeping the aquascape more or less stable from week to week. Once the roots are established, it branches readily and gets bushy. One stem is all you need to get started.
Will concur with the slow growing observation. Gave it a shot under 1.75 WPG strip tubes with CO2, no special fert regime. Not the right tank for it. Pretty much failed...does grow, about an inch per month which you can compare to the moneywort in the same tank which does almost 2 inches per week. Collects algae on it's leaves much like anubias if you have that problem.
Definatly a slow grower, having some algae problem growing on the leaves. However this plant is without a doubt the prettiest plant in my tank, and is well worth the effort. Stem grows bright red in my tank with pink leaves. I have 3.8 wpg, in a ten gallon with diy co2 and it's surviving, but not thriving
Based on a previous post, I'm not quite sure why Alternanthera reineckii is not an Alternanthera species? Anyway if this belongs in another category please remove it. I have grown Alternanthera reineckii for many years using high light, regular fertilization and CO2. Under these conditions it is easy to grow and very prolific. The color is startling red and is very eye appealing. It will grow emerged from your tank; so, keep it clipped. I have pruned one bunch into a low growing hedge by mowing it down to the substrate every month. I would say that under high light, CO2 and fertilizer, Alternanthera reineckii grows pretty fast doubling in size after three weeks.
Tons of fertilizer and medium-low light does the trick. The fertilizer contributes to the overall health of the plant and makes it produce more roots. Make sure this one's stems are spaced individually.
Regarding Alternanthera reineckii 'cardinalis' in particular, since it is one of the plants that Petsmart is now stocking (from Topfin): I wanted to second the comment that shrimp will eat it, particularly if they're lightly fed. My amanos (followed by cherries) stripped three clumps of this bare in less than a day. They're working on the stems now.