Your filter and heater should work just fine and your LED light will be okay regarding you don't want to add coral. I would recommend getting a hydrometer to check the salinity(how much salt is in the water) and a powerhead. Brown algae is very common in beginner saltwater tanks. It is usually caused by lack of circulation and the powerhead will help create a better flow in the tank.
If you want sand as a substrate, be aware that the vacuum will most likely suck it up when you do water changes. I use crushed coral in my saltwater tanks.
You want to get about 10 pounds of live rock or 1-2 pounds for every gallon. Live rock might be expensive; where I buy mine it is $5.99 a pound. You can use something called dry rock which is essentially the same thing as live rock it is just not cured and your tank will take longer to cycle. This is because the dry rock technically needs to be converted into live rock before it can provide your tank with its biological needs. Dry rock is about $1.99 a pound. May sound confusing right now but just know there is nothing you need to do different as long as you understand your tank may take longer to cycle and you need 1-2 pounds of live rock for every gallon. If you want to use dry rock, I would recommend doing 6 pounds of live, 4 pounds of dry. I used all live rock with my 10 gallon tank but my 75 gallon I did about 55 pounds live and 20 dry.
Next, you will need some salt. LFS sell boxes of salt for 10 gallon mixes but I would highly recommend getting something for a 25 gallon because you will need more salt in the future and it is always handy to have around. DO NOT dump all of this salt in your tank. Get a large 30 gallon container(I use a trashcan) and fill it with water to the point where there is about 5 gallon left. Dump all of the salt into the container. This will allow all of the salt to dissolve correctly this way it is not too concentrated when you add it to you tank. Once the salt is dissolved, mix the water up so all the salt doesn't sit on the bottom and add about 4 cups of the dissolved saltwater to your tank. Check the salinity in 24 hours with the hydrometer and make sure it is at least 1.018. This may be low for some fish and corals but it will keep your live rock alive while you allow your tank to cycle.
Like Tcamos mentioned above, evaporation is a problem with saltwater tanks and because salt does not evaporate, you can top it off with freshwater when this happens.
A myth about starting saltwater tanks is that it will take FOREVER to first cycle. Some people say to place a dead piece of shrimp at the bottom of the tank and allow it to decompose to help your tank cycle. This method will take forever; however what I do is just add the live rock, salt mix and conditioner right away, run the filter, and add a little bit a food after about three days(tropical flakes are fine.) It honestly took my tanks a week at most to fully cycle and once I got the salinity levels correct, I was able to add fish two weeks after I set it up! I set up my saltwater tanks over a year ago and my beginner clownfish are still living!
Just remember to be patient and eventually you will have a really nice saltwater tank!
