Almost two months now.
You really need to research how to keep the barnacles alive. While it's difficult, mostly because of feeding, it's not much harder than keeping any other specialized filter feeder alive, and it's certainly not impossible I feed them both zoo and phyto with a turkey Baster twice a day. Once in the am when I go to work, and in the PM when I get home. It's pretty easy once you get the routine down. This is why I suspect the sponges and tunicates have done so well up till now. (And why I am dealing with a little bit of hair algae.) Keep in mind that you will loose quite a bit of sponges exposing them to air when you put the rock in. But as time goes on, some of them may come back, and spores of ones that may not have been visible to you, will start to grow. If anything, using ocean rock will confirm what Ian Malcolm said in Jurassic park that "life's finds a way." It's pretty fascinating.
Once the tank gets more mature, I'm sure the feeding frequency will cease a little bit as the available food in the water column will become more dense. But as of now, I like them so much I've been working pretty hard to keep them alive.
Again, the tbs rock all depends on your goals. If you are wanting nothing but what you personally add to the tank, and want to keep hitchhikers to a minimum, then the TBS rock is not for you. Which isn't a big deal. People have been using dry rock for a couple decades now and have made some amazing looking reefs.
But if you are looking for instant bio-diversity and are ok with dealing with the downfalls of that, then by all means get the TBS rock. Yes you will have to deal with some "back of the bus" inhabitants, but it's the nature of the beast and really is the way a real ecosystem works. Some people don't like that kind of volatility in their tanks. They want to make something ornamental that more closely resembles what their idea of a reef should be, or have specific animals they want to house, and that's OK too. Just know what you are getting into.
I want to have a tridacna clam or two in the future, so the whelks are out the door. I chose to have something that more closely resembles an ecosystem, and I'm willing to deal with the consequences of that decision. Make sure that you are as well.
On a side note of being humane. I've been boiling water in a mug in the microwave and chucking the whelks I find in it to kill them quickly. Is this acceptable? Listen, I know they are just snails kids. I'm not a bleeding heart either, I hunt almost every weekend, and I kill my share of animals. But I only hunt to eat. I've never kept a deer head for my wall and I never will. What I don't eat goes to the homeless shelter. Nothing is wasted, and I pride myself in being a humane and respectful hunter. Even though they are "just snails", there is no point in being disrespectful to them.
