Navarchus losing color   10/3/11
Hey there folks - I have not been able to find a reference to this particular problem anywhere and was hoping you could help.
<Will try>
I have had a Navarchus angel for about 18 mo.s now in a 150 gal Fowlr. He acts and eats very well and has grown from about 3.5" to close to 5" in that time. However for at least the past year he has been steadily losing iridescent blue color in a particular pattern. It first disappeared on the margin of the tail fin, then began fading on the outline of the dark blue saddle just forward of the caudal peduncle. It is now completely gone from those two locations and is fading on the rearward margin of the dark blue area behind the head. In the other locations - the margins of the dorsal, anal, and pelvic fins, and the front of the head - it still seems normal. I have attached a pic for reference.
<See this>
He eats primarily NLS pellets - both Thera-A and color enhancing varieties, as well as various Ocean Nutrition flakes, some frozen, gels, and Nori.
Water salinity is on the low side at 1.021,
<Too low... a contributor here. Raise this to natural seawater strength>
nitrate is <1 ppm,
<How is this kept low? I.e., do you employ chemical filtrants?>
and temp is 79 F. Lighting is on the low side with only 36 watts of LED for about 8 hrs per day. There is some hair algae on the sides for browsing although he doesn't show any interest. Bioload is fairly low with only 3 other fish - a 6" melanurus wrasse, a 3.5" Lemonpeel angel, and a 2.5" flame angel. Yeah, I like angels and have found keeping multiples to be not very difficult if they are introduced gradually. The Navarchus is the undisputed alpha fish of the tank however and no one challenges him.
Other than the color problem all seems well. The fish is getting to the size where he is becoming "majestic" and he is beautiful regardless, but I would like to know the problem and reverse it if possible. Thanks for your help.
Mike
<Mmm, well, the foods you use are good, complete, but I'd mix in a vitamin/HUFA product as well... As to the real, likely root issue here, it's water quality... Are you aware of RedOx measure? Please search, read on WWM re... and we'll chat. Bob Fenner>

Re: Navarchus losing color -- 10/07/11
Thanks for your reply Bob.
<Welcome VD>
I am managing the tank more or less like a reef which is where most of my experience lies. There is about 120 lbs of good porous live rock in a very open structure, decent water circulation, and I wet skim with an old Top Fathom 200a. Perhaps a more modern skimmer design would be more effective, but I am reluctant to put money into this when the selection is fairly bewildering and seems faddish.
<Better for you, others to look into, investigate RedOx, perhaps acquire/use an ozonizer>
The bioload is relatively low. The water change rate is fairly low at about only 15 gal per month. The nitrate test kit could be inaccurate and I may take some water to a LFS for corroboration. Since your reply I am using multiple water changes to bring the salinity up to a target of 1.023, which doesn't seem that much different, but in this situation every possible contributor counts. I understand the concept but I've never employed a RedOx meter in the past - perhaps this is something I can have tested at a LFS
<Mmm, yes>
as well. Generally I've relied on keeping nitrates low and alkalinity reasonably high (my well water/make up water has naturally high calcium and an alkalinity of 300 ppm) to ensure decent overall water quality as other parameters seem to fall in line when this is done. Perhaps this is not enough in this case and I am just kidding myself here. I will test accordingly and step up water changes as a matter of principle.
I need to find a food with the vitamin/HUFA component as well. I feed Cyclop-eeze on occasion but the Navarchus doesn't eat much because the particles are so small.
<Look into New Life Spectrum pelleted food... completely nutritious and very palatable>
If I am successful in correcting whatever is causing this condition is it likely that the color will return?
<It indeed can>
Thanks again.
Mike
<Certainly welcome. BobF>