Anacharis melting?

Anachris or elodea or egeria, is a very common plant. It can be used a food for some fish (like goldfish etc) but also grows well.

It sounds like the bunch you recieved is adjusting to your water conditions. Just a warning, this plant is normally grown outdoors in ponds. In lower light the leaves are much smaller and internodes can be over an inch. It looks very different in a short amount of time.

I will also note that Anacharis is generally a coldwater plant—if your tank is warmer than the low 70s, it could very well be a heat-induced melt.

plant melt is pretty common with anacharis..
while there are some cooler water species of this plant there is one commonly referred to as Brazilian waterweed(egeria densa) tho I believe you may find this version on the 'list(invasive plants)
here (Washington State) we have Elodea Canadensis and also several lakes with the invasive densa(illegal to transport/posses)

I agree... I think the key may be temperature, because I have had a hard time with this supposedly "easy" plant in my tropical tanks as well, and the warmer the tank was, the worse it did.

First, if there is new growth on the stem, just let it do it's thing... It will indeed resurrect itself sometimes. I have also saved mine a few times by floating it until little roots pop out and then cut it just below the root and re-plant it... plant as many segments as you can cut from one stem... each root will be bury-able and a new stem will likely sprout just above it after it gets planted. Sometimes plants melt during their adjustment stage after being moved from an environment with different lighting and water parameters. It's pretty hardy for the most part, but it can be challenging to establish.

Anacharis also melts if you use Excel (glutaraldehyde)