My purple tang has LLE pretty bad. Anyone have experience with this? I'm hoping it hasn't reached the point of no return.

look here Marine Head & Lateral Line Erosion: A Description of the Syndrome and a Review of its Speculated Causes by Steven Pro - Reefkeeping.com it doesn't really answer for sure what causes it but will give you something to think about.

Giving Fish Vitamins seems to look like a good answer so long as the fish hasn't got to far, if you do want to start a Vitamin treatment, I would suggest getting a liquid form and letting the fish food steep in it for a bit, use Vitamins designed for children and not adults.

But on the article I linked maybe you can take heart from this quote

We adopted a Hippo Tang with LLE. We fed it Mysis Shrimp (frozen) and Seaweed Salad. It helped a lot. You may want to research on the proper diet for this kind of Tang. Good luck.

I have the algae...I will look into the vitamin C. I have had the tang for years along with a red sea sailfin which I just lost recently. May be due to water changes. I have read up on better quality salts and just got my own RO/DI unit. Just have to get it hooked up in between other projects! Also invested in a phos reactor because I've had an algae and cyano take over!

I popped in to Dobbies today and seen on the shelf a bottle of Vitamin supplements for fish, never noticed them anywhere before but I should have known somebody somewhere would have started making it and putting it in a bottle for us to buy, so maybe try a Fish Shop in your area to see if they have any in stock.

I live in the UK and have a 2 year old the goverment give us a liquid Vitamin for the kids which I used in my fish food, my parter wondered how it got used so fast lol.

Salt wise I use Deltec H2Ocean, Ive yet to see a bad review on it and looking at the Calcium, Mag etc etc it contains it has the right amount of them all not to much and not to little, Ive seen folks say certain brands lack calcium or another element.

Having your own RO/DI unit is very good for many reasons, it means if you need water fast and the LFS is closed you have it at hand, saves you going to a LFS to buy it and if you don't have a car it saves you carting it up the road in a bus or having to pay out for a taxi.

I was buying 2 Jerry Cans of water a week costing £7 for both, so I was paying £28 a month on RO water, my RO/DI system cost about £100 in total so after 4 months it payed for itself.

Also by owning your own system it means you know the quality of your water, when I first started SW fish I bought my RO water from the same shop for months, 1 day I tested it when I got home and it had a lot of Phosphate in it, I used rowaphos in my filter so it ended up my filter was cleaning this water I bought which was supposed to be pure with nothing in it.

I bought MarinTropic which is was rated very high as well. I think it is out of Germany. Just starting to become available here in the States but you still have to order thru major distributors. I've only used it on my small tanks because I don't have the RO/DI set up yet but I can actually dissolve this stuff in a gallon container by shaking it up real well. The other crap I was using, actually circulating for days and could still see the salt in the bottom of the container!! I thru it out...