Will the roots spread all over the terr? Most likely -- it's what roots do.

Will it outcompete the other plants? That's is always possible no matter what collection of plants you have. I wouldn't worry about it though.

The emerging roots? I would expect that that may well indicate that you have sufficient humidity and other conditions such that the plant is entering a growth phase. The additional roots would be used to gather nutrients and water to support futher plant growth. So it likely means that your Anthurium is a happy camper.

Thanks for answering, Paul! Yeah, It's been 2 months and they're doing really well in there. I think it's really entering a growth phase like you said. It has made like 4 or 5 new leaves and a flower! The only problem is some of the stems have grown quite tall and they've kind of grown into the light fixture. Is there any way to fix it besides cutting them off? I have another aroid with a similar problem. But it hasn't yet grown too tall, but in a month or so, it will!

I've read somewhere on the web that having insufficient light makes 'em leggy? But I don't think that's the problem. I've also read that I shouldn't fertilize my terrarium, is that true? Do they LITERALLY mean no fertilizer at all? I've used those "slow release pellets" couple of times cos I was told by the nursery that'd make them flower. (AND IT DID!)

I have 2 mini bonsai Ixoras too. They're both budding new leaves and one of them is even starting to flower.

Again, thank you so much for anwering Paul. After 2 months I thought no one wanted to, maybe because my question was too dumb, lol

Take care
Derek