Fish fin rot?? Uh oh..

[taemujin]

Well, there seems to be a diatom bloom in my tank. A brown colored algae that covers my entire tank within 12 hours... I've been keeping it under control by brushing it off the rocks and sand with a toothbrush.

I did notice that the brown algae smelled really terrible though.. every time I took my hand out of the water and I smelled it, I gagged. Which leads me to wonder if it is just a simple diatom bloom?

Today my damselfish came out during feeding time and half of his tail seems to have rotten away. It looks like this brown algae is growing at the edges of his withered tail....

What treatment would be best at this point?

Thanks.

 

[taemujin]

I forgot to add that he seems to have some raised white areas on his body (doesn't look like ick, more like raised white lines going up and down on his body)....

 

[taemujin]

Also he seems to have what looks like a long white stringy piece of poo hanging out...

I feel bad for him does this sound like a bacterial or fungal infection overtaking my tank?

I do have a coral banded shrimp, a few nassarius snails, and a sand sifting star in there as well; they seem to be doing fine; they move around and act like they usually do.