Time lapse of alternanthera reineckii ‘rot’

 ‘Rot’ is German for ‘red’; this plant was grown by Dennerle and purchased from Pro Shrimp.  I’m not sure if it’s the same as ‘alternanthera reineckii’ without the ‘red’ qualifier on the end.  It’s the red plant at the back left.

The plant was shipped on 1-Jun-2020 and arrived in great condition and quite a lot larger than I expected it to be.  After two months (31-Jul-2020) I thought it was growing great but now looking back at the picture, I’m not so sure.  The stem in the middle has clearly had a huge burst of upwards growth, but not so much the stems on either side.  There also looks like some bare patches under the new growth, which might be from emersed-form leaves (as almost all plants in the trade are provided) being shed upon fully-submerged growth in the aquarium.  I decided to snip off the top half (the new growth) from the large middle stem and replant the top to provide an extra stem and fill out the back corner of the tank a bit.

Disaster!  Neither the newly planted top piece or the other non-trimmed pieces ever really took off.  They just kept getting more algae on their upper leaf surfaces and becoming progressively more ratty.  I’m not sure why this plant failed to thrive.  The light I thought was good or even excessive – it was on for 12 hours per day during this time.  The tank had injected CO2 gas, and I was running estimative index fertilizers so seemingly was set up for success.  I think what may have done this plant in was the notorious green spot algae.  Alternanthera needs lots of light and grows slowly, so algae on the upper leaf surface will rob the plant of light, slowing plant growth even more and giving the algae more time to keep covering the leaves in a vicious cycle.

Interestingly, the lobelia cardinalis ‘wavy’ planted in front of the alternanthera thrived immediately upon planting and has been doing great ever since.