White in dorsal fin

Yes, fungus is a possibility.
There is probably a whole lot of fungus in the tank, but before you get alarmed, fungus is a good organism and is a natural part of the functioning of a healthy reef aquarium. We don't like it showing up on a fish, but we can do something about it.

Actually, a pic of the entire tank would help identify it and help with the treatment.
Can you show us a pic of the entire tank and maybe a closer shot of the fish in one area of the tank?
Which fish is it?
How long has it been in the tank?
How old is the tank?
What is it eating and how often?
Is there a Cleaner Shrimp in the tank?

Thanks for trusting this MB with your situation/problem.

That's a great pic of beautiful fish. It tells me all I need to know, but are the other Anthias or any other fish chasing it, even just a little?
It would need more time to get accustomed to everything and for everything to get accustomed to it but I don't recommend that right now, for this situation.

The minimal feeding to control the algae has put some stress on the fish and shrimp. They are very hungry. That's why it runs from the Shrimp because it knows they are hungry for more than just a simple cleaning.

One of the best things to do when introducing a new fish is to feed extra before and after introduction. Unfortunately, since I can see the algae is still a problem, extra feeding would not be recommended. Fish pollute the water, so they are part of the reason for algae problems in the first place.

I see some blood in the fungus on the fin. This is not a good sign. I would recommend removing the fish to a Hospital Tank and wait until more of the algae has disappeared before adding it back in.

I see by the look of the algae that it was stressed but now it is growing back. You are not out of the woods yet. How many snails are in this tank?

You may be in disbelief that I could think to know so much about the tank and what it needs, but I've been at this for most of my lifetime, and I'm pretty old.

Nassarius snails don't count. They don't eat algae. By Mexican Turbo snails do you mean these which used to be called Margarita Snails, or are you talking about the large Pacific Turbo Snail?


To tell you the truth, if not Pacific Turbo, that's less than half the algae eating snails that I would have in that size of tank. Without more snails, algae grows unchecked. Hermits can become a nuisance and cause trouble. I would remove all but 20 of the Hermits, trading them for my best recommended snail ratio, 50% Astrea, 30% Margarita and 20% Cerith Snails.

Did you acclimate in a container to see if any fish showed aggression prior to releasing that Anthias into the tank?
Angelfish are territorial. The lack of supplemental feeding to control the algae growth has caused it to more aggressively defend its territory. A major food that the Angelfish is not getting is soft surface algae. There is little of that right now. The algae eating Blenny is also suffering.
Fish don't bump into rocks like you may be thinking. Illness, including fungus typically becomes a visible problem when the fish is stressed. Fortunately, there are some things you can do to relieve some of that stress.

I'd get the fish out to an established hospital tank and feed it well.
Speaking of feeding, if moving the fish is not practical right now, you may have to temporarily accept increased algae growth in order to try to save that fish. I would suggest doing a complete switch of your feeding. I feed frozen meaty food every day, with a fast one day/week and leave the dry food for when I don't have time to thaw some frozen. Follow the directions found in the Reefkeeping Tips for adding aq drop of Garlic Oil to the frozen meaty food once each day for the next 10 days. Also feed twice/day for the next week or so.

Oh and if you can add 100 snails, do it.

Any questions? Please keep in touch, call if you need to.

Just an update, it looks to be going away.  

Alright here is one of him tonight.  Basically all better!

^You know what is crazy? Like almost all of the green algae is gone now. I changed nothing. 

That's wonderful.
The 40 Turbo Snails were good ones and they have been eating at night.
Most snails are nocturnal. If they don't have enough to eat they will start cruising in the daytime. There was a lot of algae and now with it gone, 40 big snails will push all over to find something to eat. Now is the time to consider whether there are too many. Removing some is a good idea, before they starve to death. There are always hobbyists here looking for snails.
Remove any that die, ASAP so they don't add pollution back into the water.
It's a balancing act.
Keep an eye on the LR. If algae starts to come back, even just a little, add a few snails before it gets out of control.