I think you are comming along and well on your way of owning a saltwater tank! Angel brings up good points that we all have to be mindful of. I don't think that you have stepped over any line that any of us haven't done while at the beach. I know I have a few jars of sand and some shells (some that had inhabitants at the time) from beaches I've visited.

My advice at this time would be to keep an eye on the LR in your 10 gallon. Don't remove anything until it smells bad or generally appears to be dead. Sponges in all their glory are always a good thing to have. If it is dead then they usually just melt away in the water (what doesn't dissipate you can try to remove if it is dead).

My second thing would be not to mix what you got at the local beach and what you are trying to make for your 10 gallon. The composition could be totally different and cause a crash of your system or many other problems that would take me forever to list. Watch it in your pico if you choose and see what happens. Its a small enough tank that if things don't go right after a couple of months your not too invested. Then again it may go wonderfully and you can share your experience with us.

If you can keep the plant growing I would keep it. Plants in a reef tank are a great addition as well as helping keep things balanced. Since it's not a nucience algae your ahead of the game. Good luck with it and keep the pics comming. I like how you set up your tank. Hold on cuz if you thought you were hooked before it only gets worse once the tank is wet!

Angie