So java moss 'roots' or grabs on to things like java fern eh?? So what sort of maintenance are we talking about.
Well, if you ever want to get it off of a rock, pretty much, your only option is to burn it. One time, I had some java moss get really really stuck on some rocks that I took out of my aquarium. It was left sitting out of water for probably a month; then I gave the rocks to a friend, and to my amazement, java moss began to grow off of those rocks. I'm pretty sure that's not even physically possible, but I swear, I saw it happen.
I do have a sword in there & plant to get another. If it doesn't have roots in the conventional sense how does it sap all the energy from sword roots??
Well, here's the thing; like anything else java moss gets near, it will latch on to that sword and pretty much never let go. In the same way that algae can kill a beautiful plant (as brown algae is doing to my gorgeous anubais; the water here is loaded with silicates
) it can just sort of take over. I have actually had a mini-sword be murdered by java moss. Really, it is a wonderful plant if you're cheap and lazy and don't really want a full time planted tank, but I can not stress enough how much I think it is a bad idea to put that water weed in an ambitious tank.
However, that's just my opinion, and I'm sure plenty of people will disagree with me. If you're willing to be VERY vigilant with that stuff and keep it in its designated place, you shouldn't have too many problems. Although, I'd wager that from your fish knocking it around, after about a month, you'll have 3 or so balls of it growing in other parts of your tank. But again, if you load it down with gravel to hold onto, even that shouldn't be a huge issue.
There are LOADS of alternatives that will look great; any runner will do. However, you might have to "mow the lawn" every once in a while to keep that nice look. I've had varied success with these kinds of plants, and really, it just boils down to the water you're using.