Beginner needs help

Actually fish are easier to keep the inverts like urchins and mushrooms, so you want to start there. It also helps to get a list of what you want to have and then post it here

What size tank? That will determine in some part what else you'll need. Also, review what type of urchins and other inverts you'd like--some are hardier than fish, some are currently impossible to keep for long.

Here's how I would set up the tank:

I'd start with at least a 55. I prefer 65's, better shape, but a 55 would work. I'd add the substrate--I like sand, it's easier to maintain, and keep clean. I'd then order about 75 pounds of Tampa Bay live rock--it comes with a bunch of cool hitch hikers, and likely many urchins already. For lighting, I know I'd go with metal hallide, simply because it looks so much better, and gives you a wider variety of options down the line for corals and clams. I would run a skimmer, simply because it makes it easier to keep the tank in good shape. I'd put in 3-4 powerheads, about 1 every 18 inches, but probably have a variety of sizes to create different levels of current in different parts of the tank. A good heater, and you're set. I'd probably plan on getting a reef ready setup so I could put in a sump easily, and put all the equipmet down there, in addition to having an automatic FW topoff system.

This is pretty much what I'm planning for my next SW tank. Stock will be mostly inverts--shrimp, a few crabs, lots of snails, a few urchins, and lots of encrusting corals. Only fish will be some gobies, maybe a mandarin down the line.

Depends on your definition of 'inverts'. Most of us lump corals and crustaceans, gastropods, mollucks, etc all in the invert group. Technically, they are all inverts. But, many people use 'inverts' to refer to mobile invertebrates. Most mobile invertebrates: crabs, shrimp, worms, snails, urchins, stars, etc will be fine with just a plain old NO strip light. Inverts like corals (brain coral, polyps, zoanthids, anenomes, etc) are primarily photosynthetic, and do require lot os light. Deeper tanks, like standard 55's, can be tough to light well without going with something like metal hallide.

But--if you already HAVE the strip light, you'll be able to keep most mobile inverts. If you later decide you want to start adding corals, you can upgrade later without it costing more. You'll just have be certain the animal you're purchasing doesn't require high lighting--fairly easy with adequate research. I started with strip lights, then went the VHO, then to MH--and would have saved mucho dinero had I just gotten the MH to begin with.

I'm a fan of skimmers. They are not a requirement--I'm running tanks currently without them. But--without a skimmer, you end up needing more frequent water changes to remove wastes that can cause water quality problems otherwise. In smaller tanks, this tends to be a bigger problem than in larger tanks.

Mixing pool sand and live sand is fine. Or, you can use all pool sand and get a live sand activator kit. Or, get really good live rock and no live sand--most of the animals that colonize the sand will come off of rock just as well. Live rock needs to be porous-dense stones do support the same quantity of bacteria (less surface area). Lace rock is good, and can be used to make up a portion of the volume (say, 30 lbs of live rock and 30 pounds of lace rock). The critters, good algaes and bacteria will colonize every surface in the tank, it's just a matter of what objects provide more surface area for them to move on. Making your own from concrete is an option, but it's pretty labor intensive, and requires lots of curing time to avoid water chemistry issues.