Frag tank

[Needles15]

Do I need to cycle a frag tank?

 

[mr_X]

Are you connecting it to the main tank? If so, no, you don't. If this is a stand alone tank then yes, you do. You will probably have a fish in it, if not your corals will not do well without nutrients. If you feel you are going to add food to the water column for the corals, then you will still need to cycle it so that this food can be processed.

 

[Needles15]

Okay what fish do you recommend for a 10gal, and should I have some LR rubble or bare bottom?

Could I use half new saltwater and half out of my display tank? They won't be connected

 

[mr_X]

You don't necessarily need rock or sand in the tank. That's up to you. I see a lot of people using a small wrasse in frag tanks. I suppose they feel it would help with any parasites from new introductions. A 6 line wrasse is pretty popular.
I would probably put a couple rocks in there just to give it some cover.
Yes, you could use water out of the display if you liked. You would still need an ammonia source to start the cycle.