'Naked' stems

It may depend on the plant. Most of what i have seen is that they will continue to grow, or become a floating group of plants after a while.

What about rotala indica? and some of ludwigia species?

They will be ok. The rotala might rot of at the gravel and float up but but sp generally wil produce many side shoots. If hte tops are not doing well amd producing new growth then you probably have a/some nutrient defecincies that will need to be dealt with.

Can you give us some more info about your conditions, especially lighting, tank size, and fert regiment.

Hope that helps

Anyone?

EDIT: The Picture showed up for me now..

In extreme situations, the bottom of the plants may completely melt away. However, the growth tip should always remain salvageable. You may want to add more light, but I recommend adding CO2 along with the extra light. Otherwise, the aquarium will probably experience an algae outbreak.

Carlos

Thank you.
By the way, does the health of the bottomed leaves depends only on light, or also to other components, such as CO2?

CO2 and nutrients. Nitrate and Potassium are big ones. With nitrate deficiency, the older leaves turn yellow. With Potassium, the older leaves get pin holes.

Hope this helps!

Carlos

It does
thanks

As long as a good portion of the plant receives the appropriate amount of light, shaded areas should not deteriorate. Of course, I assume that the plant's nutrient needs are being met. You can see this with Dutch style aquaria where the dense planting shades the lower stems but the plant is very healthy.

Trimming with this type of issue (for stem plants) requires that the stem be cut and the healthy top piece replace the shaded bottom piece by replanting. After a while, you will get the hang of it and it shouldn't be too dificult.