Entangled

I dream of dark-haired girls.

My fish tank of late is a fairly advanced eco-system that contains fish, snails, and plant life. The snails cleanup the tank, a clown loach keeps the snails in check, and the fish live off of the plants and the fish flakes we liberally add to the tank on a thrice daily basis. The plant is the reason I bring this up, however. It's a tough-stranded lifeform that grows quite fast, and takes up quite a lot of space... choking the fish and the filter if large portions aren't removed regularly.

I'm obviously too soft when I keep a reserve tank where I transfer the removed plants. Reasonable people would just throw the stuff out.

There was another plant in the tank originally, a sort of broad-leaf underwater grass. It lived, but never thrived, surrounded and swallowed by its fast-growing skinny cousin.

I don't want to completely remove the plant life, as it serves a purpose, but it is dangerous if left unchecked.

This all reminds me of my love life, and how something planted long ago, that can't be removed because it has a purpose, sometimes overgrows and chokes off competitors that I prefer the look of.

Clarification:
I prefer the look of dark-haired girls. Therefore I am saying that my concern is that future relationships with the dark-haired girls I dream of will be choked off by someone whose relationship with me started deep in my past.