the sponges are very beneficial to the system. so those are bonuses....the small anemones look like aptasia which is no bueno. i would try to kill them off quickly before they really over populate your system...and that 4th pic of the algae looks like Bryopsis, which is also no bueno...
heres a lil write up about bryopsis..
"Some of the hardest to remove common species of macroalgae encountered in the hobby are B. pennata and B. plumosa. These two species have noticeable discernible midribs (center portion of the algae), that are wider than their branches. They also form a mat like root system on the rocks.
B. pennata (pictured on the left) has irregular and more sparse branching than its closely related cousin B. plumosa which has more symmetrical and fuller branching. (picture coming)There are many, many species of Green Hair Algae that have feathery branching, and are not necessarily members od the Bryopsis genus, nevermind B. pennata and B. plumosa. Simply because the hair algae in your system has branches does not mean it is one of these algae species.
The reason hobbyists despise finding this algae in their tank is because cleaner crews rarely finish it off when they snack on it. Sea hares, nudibranchs, urchins, emerald crabs, chitons, and even the larger Astrae tuber will nip at both of these species, but rarely consume it with any effectiveness.
If you do confirm you have Bryopsis:
1. Try to get on it quickly. If it is only on one rock remove the rock, remove algae, starve of light in a QT.
2. Manual Removal - If that doesn't work or get it all, remove all you can by hand. People will tell you not to do this because it will spread. Let me assure you, left untreated bryopsis will spread. Just be careful about it, and if you can pull the rock out to remove it all the better. If takes hold in the sand sift it out with a net. If you don't remove the base of bryopsis you are wasting your time.
3. Starve it out - As always if you can get down nutrients nuisance algae has a harder time taking hold, or coming back after manual removal.
4. Repeat steps 2 & 3 aggressively.
5. If that doesn't work try raising your magnesium to very high levels. I don't want to be blamed if this causes losses in your tank, many people have done this with great success and minimal stress, but still....please do your research and don't blame me if something goes wrong."