1)You don't really have to worry about hit hikers from live sand. Most of what is available now is not live sand like you are thinking of, it is biologically active, meaning it has the beneficial bacteria, not other benthic life. The type of live sand with critters is unfortunately very difficult to find. It requires work, space, and energy to maintain, so with these bio-active sands available (and labeled as live sand) it has become more cost effective to carry the bagged stuff instead. I personally would prefer the old school stuff that actually has beneficial organisms to consume ditritus and to keep the sand bed stirred. The companies that do sell as bed organisms charge astronomical prices.I also wouldn't spend my money on the painted purple rock, I'd rather go with aquacultured live rock, but you still do run the risk of unwanted organisms. I had the unfortunate luck to not even get the wanted organisms (pods, worms, etc), but at least I didn't get any pests. It is typically (but not always) cycled in systems that doesn't have other live rock, so it usually won't have life, good or bad, other than the bacteria. The benefit is that it is already cycled, so when used in conjunction with live sand, the tank is pretty much immediately ready to start being stocked. The rock also looks like it is already covered in coralline, which may be reservable to some. I find it looks artificial and isn't really worth the cost, but that is just me. You can always get a single piece of live rock with coralline (assuming you can find a LFS that doesn't carry the purple rock) to scrub over your tank to seed the coralline spores. You will get some coralline with frags as well, although admittedly it does take forever for it to get established this way.You can cycle the rock using pure ammonia to avoid adding things to decay to start the cycle. Look up fishless cycle with ammonia to get better ideas on that. The live sand alone may be sufficient if you go with dry rock and start really slow, but cycling the rock will be better in the long term to start everything off more stable. You will probably want to rinse the dry rock well to get rid of dust and possible decayed organisms. You may want to keep an eye on phosphates as well to verify nothing is leaching from the rock. Another benifit of the ammonia cycling is that it will not add phosphates, not that O really feel that cycling with food would really drive phosphates up that much, but some people are overly cautious about phosphates. Although phosphates can be an issue with SPS dominated tanks.2)Pretty much all of the soft corals or even a few SPS/LPS corals would be fine. The less expensive frags are not overly demanding. It is when the tank gets dominated that it becomes tricky and you need to monitor parameters a lot more closely and consider dosing. With a smaller tank you can manage parameters with frequent larger water changes, but a few frags shouldn't require major changes in your routine.I would definitely avoid things like Xenia and some of the faster growing mushrooms, and the like. They are easy to care for and look amazing, but can easily take over a tank to the point where it becomes too frustrating to manage. The faster growing, more common, mushrooms can usually be managed by keeping them on an isolated rock, but if they detach and move elsewhere, they can become a problem. If a bit of their foot gets left behind, new ones will retrospect. Xenia will over run a small tank. They are quite prolific and will appear all over the place. They have become a nuisance and are over taking reefs in the Carribean where they are an invasive species and have no natural predators or parasites.Zoanthids, pallys, ricordia, duncans, etc are all good choices. You can go with some bigger species than I can with my tank. I am not sure if leathers are a good choice as I am not sure how aggressive they can be. Acans are another fun one. They have some cool colorations and are fun to feed. They will take food directly from a pair of tweezers and close up around it and pull it into their mouths. They reproduce and grow fairly well, but are not overly prolific.I would love to do star polyps, but they are very aggressive and have very long sweeper tenticles. Some people have claimed to do well with them in smaller tanks theorizing that they are less aggressive due to the smaller water volume and how quickly chemical warfare products build up in the water, but I would rather not risk it. They are also fast growers as well and can quickly over run a tank.3)Not really sure on suggestions for dips. I haven't really dipped anything yet and I have been lucky, or so it seems so far. I just dropped $100 (probaly twice what I have spent on everything else combined to this point) on three small frags and even though I inspected them with a 30x magnifying glass, I am a bit nervous about one of them and have had it isolated. I don't have a quarentine and I am working on getting something to treat what I think may be on there, but this method won't treat for everything and it may be a bit risky using it as a dip.Not all dips will work on all pests, so what you want to use really depends on your livestock and what you have for corals. Some people just do a fresh water dip and call it good. It does work on a lot of stuff, but not all corals handle it well. Somebody else may be able to better suggest something else.4)Dimensions on the tank may help get more direction there. Tanks vary so widely now that the old guidelines no longer apply. A 30g cube will require a stronger light than a long shallow 30g tank, and the long shallow tank will require a longer more spread out light than the cube. You said you will be sticking with soft corals, which typically require less light, but do you want to get something that will possibly support hard corals down the road if you end up finding out you like SPS? You also need to figure out if you want to spend a little more upfront for LEDs, which don't require bulb replacement (no bulbs to replace every 6 months to a year) and are usually dimable/adjustable. Depending on your tank dimensions, you may be able to get away with some non-aquarium specific LEDs that will work very well for soft corals for very little money. T5 flourescent bulbs are another option, but are a dying technology. A lot of companies are still supporting them and making fixtures, and will probably support them for a long time, but for how long is a major question, probably not enough of a concern to effect your decision though. Power compacts are pretty much extinct. Metal halides are another option, but consume a lot of energy and put out a lot of heat and are overkill for soft corals especially on a tank your size. There are some other options as well, but LED, T5 (or T5 high output (T5HO)) and metal halide (MH) are the standards right now.Others would be able to help you better with pump and circulation questions, but they will probably want to know if the tank has an overflow, if you have a sump, and if the tank is drilled for returns.I have no experience with anemonies so I can't help you there.
