You will simply need to get better lighting, or arrange your plants in a "triangle" type of layout with the apex (tallest) being toward the center of the lighting for your high-light loving plants and your sides only used for low-light loving plants like your crypts, lotus, and such. You just can't let those rotalas grow wild, or any of your fast growing stems for that matter. As you know now, they will intertwine with everything else, shade it out, and make it look leggy, or kill it.
Try what I do with my Rotala 'Colorata' in my thread...you should be able to maintain and shape it as long as it is getting CO2 and ferts (which it is). Trim it once a week, and pretty much all the rotalas should be able to handle that. You will need to "top" and replants every few months, but the nice thing about rotalas is that they are a cheap plant to experiment with, easy to grow,and most are pretty tough. I love mine!!
LEAVE THE PARVA ALONE!!!!!!
oh i know better than to disturb the parva... it only took me 6 months to wake them up lol. i'm referring to uprooting my bunched stems only. i decided to RAOK the rotala tops and seriously contemplating wether or not I keep the evil stump or position it somewhere else. i still have the strong flow problem where in my outflow pipe is gushing that backside of my tank making it impossible to plant tall lanky bunches.
my option is to reduce the flow using the ball valve or diffuse the water by tie-wrapping filter media around the outflow idk yet. maybe i have to change the position of the outflow all together
the other alternative is what i've been contemplating for a while... EDIT.
i know i don't want to either but... ever since i threw the co2 in there the game totally changed. the plants are growing more rapidly yes but they are also more light/nutrient demanding. the base of my stems become ratty as not enough light reaches the bottom due to over crowding.
again i feel the speed of the flow in my tank isn't helping. i've read some plants have a harder time from extracting nutrients from fast water. i tested this out with one of my erio types where i placed one near the outflow and the other just floating on the adjacent side. the plant next to the fast flow turned brown.
conversely the plants that are thriving the best are my slow growing rooted plants.
most if not all of my crypts are thriving and my bulbs are doing very well.
right now, literally since this morning i have been staring at my tank thinking about how to edit species of stem plants. my tank looks like a war zone right now but i am leaning towards the economic factor in making decisions.. i have plenty of cheap stems and very expensive ones (i realized).. i may have to focus on cultivating the rare difficult stems first and throw the weeds in the grow out tank or i might just leave all of them bunched and floating till i figure things out.
OR i setup a new 100g and ALL my plants can be happy lol.