This is one of those "be careful what you wished for situations". You wanted the Vals to grow, and it sounds like they did in a big way.
When it comes to rearranging, Vals are incredibly hardy. The only problem I see is that sometimes the a few leaves will pull off easily when you are moving them around, but just as easily as they pull off, they'll grow back.
When the runner plants start to have leaves that are 2-3" long, you can cut them off from the mother plant, and then move them/reposition however you'd like. At this point, you can even take them out and trade them/throw them away if the Vals are starting to outgrow the area you'd like them to be in your tank.
And as said above, they'll be fine in the lower light situation. If anything, it may help you from having to prune so often.
They should do ok. Will probably slow down the growth a little. To move them, dig down in the gravel, under the roots and gently lift vals up a section at a time until you have the entire plant exposed. Of course you can split them if you wish. No harm.
there is no controlling them. I planted a few of them in an old tank that I left alone for about 4 weeks. With 4wpg and co2 nearly the whole tanks was vals by the end with almost no surface that wasn't blocked by them. I have since removed all vals from all my tanks. they are an infectious weed.
I just posted a similar question. One member told me I could trim the leaves down on a slant. I did. All is well. I also moved them to the side of my tank. Neither foreground nor background. They are sending shoots to the middle. I will be moving these to the other side of the tank today.
Good luck.
These people know what to do. :^)
i have the same the problem, i started with about 3 vals mow i have over 15 vals of different sizes. i might trade some here or store credit at my lfs.
Have you seen a tumble weed, or maybe even just a bundle of wires, that is what vals look like if not trimmed daily in a small tank(under 55g) I have the same issue, just trim them near the base, they recover qickly and are very prolific. With the plantlings they make great ground cover if forced to stay small like a bush.
P.S. First post in a few months shrimp tank about to get a new string of pics.