Keep watching those runners closely, it might end up in other carpets too, as it does for me i find it in the Monte carlo growing next to it. I have no experience with using deviders in the substrate, but i guess it can prevent some runners going into the wrong direction. Next time i set sometging up with different carpets with Eleocharis i definitively going to try some substrate deviders to see how that works out. I also experienced eleocharis growing so dense it was smothering itself i becoming a dirt collector. So dense and growing into eachother it was difficult to trim it because every leaf lay intangled growing horizontaly, older leaves dying of went yellow and started melting and catch algae. After a year i realy had to thin it out and then when i started pulling, rather a lot came out at once. Anyway 2 x quadrupled the amount of eleocharis i initialy planted.
A runner very inocently starts like this and can also grow where you don't like to have it.
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But in the end this same runner will turn into this. Every single leaf becomes a complete dense plant still attached to eachother by the runner root. Several young runners like the above can grow very close together and then it will become very dense. If it becomes to dense and you need to start pulling.. It's fun and scary at the same time.
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