If you are looking for a completely bomb-proof stem plant that grows under maximally abusive conditions, hygrophila polysperma might be your best pick.  I picked this up from Maidenhead Aquatics without knowing anything about it other than it looked pretty in the store.  I wound up planting it in a mix of Aquasoil overlayed on Biohome biogravel and this plant thrived.  Doesn’t need CO2, doesn’t need much light, doesn’t need any fertilizer, in other words, perfect for a low-tech tank setup.

Why don’t I have it anymore?  Well… I switched to a high-tech tank setup with injected CO2 and brighter lighting and the hygrophila went ballistic.  Every week I had to cut off and throw out huge chunks of it, it grew so fast.  It also got a bit leggy, and rooty and wasn’t the most pleasant thing to look at, which combined with its high maintenance meant I decided to get rid of it.

Great plant for setups when absolutely no other plant can make a go of it.

Hygrophila polysperma in the background (echinodorus radicans in the foreground)

 

 

 

Hygrophila outgrows the echinodorus big-time (notice the upgraded light source)