There are different species of pygmy swords the two most common are broad leaf (Echinodorus quadricostatus) and narrow (Echinodorus tenellus). Sadly I think I have Echinodorus quadricostatus since the leaves are nearly the same width as dwarf sag.
Hum I found this:
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Pygmy Chain sword grow in a wide range of pH. Optimum pH for growth is between 6.5-7.5 but it favors neutral pH a lot. Optimum temperature between 68-84 F.
myfishaquaria.com
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What are the differences between pygmy chain sword vs dwarf sag?
Dwarf sag is also called dwarf Sagittaria. Most of the time this plant may also get confused with the pygmy chain sword thinking both plants are the same.
No, It is not true.
Dwarf Sagittaria has a white bottom with lots of white color roots where it can not be seen in Pygmy plants.
And also it has horizontal lines on the leaves from bottom to top where you can not see horizontal lines in the narrow leaf chain sword.
Both these plants are well suited for your foreground of the tank.
These Sagittaria differ by overall color and size. There it has light darker green and pygmy chain sword with a dark green hue.
So I think you may have got the point.! Now you have the knowledge to identify Pygmy chain sword from the dwarf sword and dwarf sag.