unknown algae help need it

[Skimmer Juice]

wow thats allot of flatworms. I would definitely syphon them out before doing flatworm exit , there is allot there so there will be even more in the rocks/hiding, as mentioned they are toxic when they die.
I would also add a wrasse if possible , or you could look for velvet nudibranchs they will eat them . The velvets will also die when you run out of flatworms . I had the same ones from bringing a single ricordia from a lfs home . Its been a long battle but I did not want to use any chemical's in my tank. So I have been just syphoning them out everyday I just get a small tube and start syphoning as many as I can see that day , 2-3 times a day , if you use a small hose you will not take out much water I also added a yellow wrasse and he has been a big help , you could also try a target mandarin as they can help but are hit and miss. Good luck.