You do not need live sand. the term "live" just means covered with bacteria. Any surface will become live eventually.
Aragonite based sand is used because it helps to steady ph. You can use any substrate you want, but I prefer to make it resemble a slice of the ocean, or as close to that as I can, as does most people that move into salt.
I suggest you use a fine sand if any, so you don't have to maintain it. Using your gravel, it will have to be vacuumed on a regular basis.
Rock from the ocean is surface area, plus it has low oxygen zones deep inside it that also house anaerobic bacteria, which process nitrate into nitrogen gas. This rock has been deemed "live rock" as a result, and is an excellent filter. The suggested amount is at least a pound per gallon. This is why Bill came up with 40 pounds. Try to choose rock that feels light, and appears very porous if possible. Stay away from dense boulders if you can.
If you did a fish only, with live rock( also known as a FOWLR
), you don't need to be as precise. If you are dead set on an anemone, you'll have to purchase strong lighting and you'll also have to be a lot more careful with your water parameters.
Clown fish do not need
an anemone, so you can use something else for them to hide in without consequence.
The same goes for inverts like snails, shrimp, crabs, and starfish. These are sensitive creatures.
What else do you need? A salt water test kit. API is fine for the basics.
You also need salt. Virtually any salt will do.
The purple on rock is a calcium based algae called coralline. It comes in many colors, and will grow everywhere in time. You don't have to buy rock with coralline on it. As long as you have a little bit somewhere in the tank, it will grow.