You have several issues here. One, pointed out by others, is the three clowns in the tank. The other issue is the anemone getting torn to pieces. I'd guess that it had a run in with one of the circulation pumps you have in the system. Most likely it was moving around the tank looking for a better spot. To prevent a crash, you'll need to get the pieces out of the tank. Most likely, you'll also need to make some major water changes, and filter the water with carbon.
You also have some additional issues with keeping anemones. They require well established systems with top quality water, and very good lighting. You don't mention lighting in your post, so I can make no judgement about that.
Your signature mentions a Fluval 405, which is a canister filter and a Reef Octopus 100 BH. IMO, these products are not capable of maintaining the quality of water needed for an anemone. The Fluval 405 is rated about 340 gph. This is only about 2/3 the water flow you would want through the filtration system. It's only about 4x per hour. Ideally you'd want at least 5x to 6x per hours of turnover. Many people used a lot greater flow. There is also the issue of canisters on reef system. While you can use them, they are far from ideal, as they tend to become nitrate factories and big oxygen consumers if not cleaned at least once a week.
You also mention a Reef Octopus Skimmer. It's only rated for a 60 gal tank. Skimmer manufactures tend to be "very optimistic" rating skimmers for much larger tanks than they are capable of supporting in the real world. Ideally you want a skimmer rated by the manufacturer for a tank size at least double of what your planning on running it on. In other words, this skimmer would be ideal for about a 30 gal tank.
I don't know for sure, but it sounds like your tank has only been set up a short period of time. Usually you want to have the tank running stable for about a year before you add an anemone. This means no measurable ammonia, and nitrites, with the other parameters being more or less stable.
Now I know that this post sounds a bit like I'm beating up on you. I don't intend to do this, but I also don't think your going to be able to keep an anemone for any length of time without some changes to you system.
If you really want an anemone, plan a major upgrade to the filtration system, and possibly your lighting.