Water sprite (?) stems

 Earle Hamilton wrote:
>>At any rate, the water sprite will in time grow right out the top and
>>when I pull these monster plants to throw them away the plant is
>>typically 24-30 tall with 8 inches of root.
>>Here's my question.  After it is growing for several weeks some of the
>>stems develop an area that looks like something is eating them.
> ^^^^^
David W. Webb wrote:

>Based on your description, I'd guess that this plant is Hygrophila difformis
>>(Water Wisteria) rather than Water Sprite (a Fern).

Earle and David,
I think this sounds like Ceratopteris thalictroides. When I had it in my
tank it grew large rapidly and had exactly this problem with the stems. The
areas were black and the stems usually remained hanging on by a thread and
continued to grow. It looks a lot like Water Sprite -- some stores around
here sell it by that name. My H. difformis has never exhibited this

in hot (well, for here) Vancouver (80 F)