you probably shouldn't put any more anemones in there for a while. They really should be in a well established tank, 1 yr old or better. Also, if you go with a sea hare, make sure it doesn't suffer the same fate as your anemone. If it get sucked into a filter, it'll probably kill everything in your tank. I would get a RO/DI filter and make your own water. It'll clear up the alge, and be cheaper and easier than going to the store every time you need water. Good luck.
bill