Scrap the water in the tank. Starting out I would probably just buy premix from the LFS and take some time to research which directin you want to go with salts (which brand, do you want to use an RODI unit, etc.)Take everything out of the tank and give it a good rinse. You can put the LR in right away. There are a ton of opinions on substrate, but just about everything will work with caveats (too fine and it blows around, too course and there are some animals that won't thrive). PC lights will be OK for most simple corals (zoas, toadstools, etc), but you may have some difficulty with an anemone. PCs also tend to put out a pretty good amount of heat for light, so you may want to consider a lighting change if you're going to get more serious about corals/anemones. I removed the bioballs in my BC29, they just trap too much crud and aren't easy to clean.