I tend to agree with eveything said here. Corals and inverts typically do not have the same impact on bioload that fish do, and corals may actually have a positive impact for the fact that many feed off and absorb nitrate. The reason to be careful adding is two fold. They are basically intolerant of amonia and nitrite, compounds that could potentially be present in a newer tank, and can be expensive to buy and replace if your system isn't quite ready. If you can detect no amonia or nitrite, I say buy as much as you're comfortable losing if something goes wrong, the swap is going to be about as cheap as they come. This will basically always be the case as even established reefs can have unforeseeable issues. As a beginner, it wouldn't be a bad idea to stick to the more forgiving types as you're still learning how to keep a stable system, placement, etc. The lps listed can potentially host clown without issues, but if they are still establishing or if you get a particularly rough clown, it might be a problem . I'd recommend getting your hands on a tank raised nem, which are typically as hardy or more hardy than many corals, or possibly a nice large toadstool coral. The toadstools have nice long polyps and will quickly acclimate to a wiggling clown.