Adding a Yellow wrasse with a Six line? Controlling Flatworms

[Squanto804]

Is there any problem adding 1 or 2 yellow wrasses to a 300 gal reef that already has a six line? I'm using them to help control flatworms and was going to add a couple more six lines but people keep telling me that they probably will become aggressive. I was told yellow were pretty good at controlling flatworms.

Thanks for any input.

Scott