I've been fighting a NASTY outbreak of Bryopsis for nearly a year. Now, I can happily say it is nearly gone. Not knowing where it came from nor how to get rid of it, here are the changes I made along the way, all the while hoping against hope that something would make a difference. In the end, I think each of the following had an effect on it's dwindling away.
The first thing is to attack it with fingers, tweezers, anything to rip if out of the rock. In my 135, I could collect one half a beer pitcher amount two days in a row. After about two hours of picking the dreaded crap, I would quit in disgust. The next day, the half side I picked was such an improvement, I'd do the other half. BUT, you can't strip it bare and in a month it was back, even worse. After many months of this, it was clear the Bryopsis loved my tank conditions. YUK!!! However, harvesting it is a form of nutrient export. How many times have we heard or read about the importance of nutrient export?
Second, my CUC was a little sparse so I added 100 hermits from IPSF of Hawaii. They seemed to make a dent in the Bryopsis but it was still out of control. My picking, ripping and swearing events were now only every 6 to 8 weeks apart. Progress in any form, is still progress.
Third, a friend gave me a small clump of red algae for my
sump, which had a small clump of Chaeto also. They both were about golfball size. They didn't seem to be growing under an old (30 yrs) 14" fluorescent lamp. I bought a new bulb, a "sun" lamp. It didn't seem to make any difference to the "good" algae.
Fourth, a friend told me the tiny hermits he collects in the Keys eradicated his problem algae in about a month in his 75 gal. GREAT, now I just have to drive 4 to 5 hours, one way, collect 100 of these little hermits and...wait...gas at $4 a gallon...probably an overnight trip...not a chance. OK, where can I buy some Keys Hermits??? Well, didn't have to. About a month ago he called and said he was returning from the Keys and did I want some hermits? DID I??? You bet! He stopped by and gave me about 75 (didn't count, guessed) tiny Hermit Crabs. I looked at them and thought, they are not going to make a dent in this Bryopsis crap.
Fifth, I noticed my two tangs (7" Sohal and 5" Desjardinii) would pick at the algae for a few days after I thinned it out. I held back on feeding Nori for a few days after thinning the algae. When they turned their noses up to the Bryopsis, I gave back their Nori treat.
Sixth, I introduced several Atlantic Dwarf Sea Hares to no avail. They did their usual disappearance act. I also introduced an urchin. He just picks up shells and zoanthids on his back and carries them around like decoration. Kind of reminds me of Minnie Pearl's hats. Don't know who Minnie Pearl is??? Man, you are young!
The urchin turns out to be a good bulldozer, toppling my
frags.
Remember that when you think about getting an urchin. It's not that they are all bad, just keep that in mind.
Now today, I'm ecstatic to report, the Bryopsis is nearly gone. There are a few spots of it that are hanging tough but, not a problem like before. I can now pick the bulk of it in about a half hour (being leisurely about it), the tangs come by and pick a bit, the hermits are doing their thing and I am enjoying a clean aquascape again. OH, the red algae and Chaeto in the
sump have multiplied into nice sized clumps, too.
Bottom line thoughts on this event is this... Our "systems", taken in their entirety, produce nutrients in abundance,
Nitrates,
Phosphates. If tested for, they show up. With regular water changes they mostly remain in check. Allow an algae to get introduced and it will begin to utilize the nutrients. That's why our tests eventually come up 0
ppm. This is good, when it's a desirable algae, not good when it's a nuisance algae such as Bryopsis. My Bryopsis was growing at an equal rate it could get nutrients. I suppose Phosban and reactor might have been the answer. But that's another on going expense I didn't want to aquire (this hobby has enough of those). Plus, we've all had successful reef aquariums that didn't have nuisance algae outbreaks. I knew once I eradicated the Bryopsis with herbivores, pruning and alternate nutrient absorbers (desirable algae in the
sump/refugium) the problem would go away. And, it is going away.
Problem algae is a double edge sword. You hate when it arrives but, it is a sign that something is out of balance in your system. Look for that imbalance, correct it and you are on your way to eliminating the problem algae.
I hope the above scenario has given you ideas and hope.
Dick
icon under their name to add to their reputation. 
