Looking back on what may have caused this???????

I'd go with HUGE fish load and a HUGE feeding regimen!

I'd also say that this is not a problem for the last 4 weeks. Look back at all of the pictures you have taken over the last 6 months. In the fish department, what's left and when did you lose it?

In the last 2 weeks, I have added 8 fish. I'm paranoid that now I have too many. I'm around 30 in a 500 gallon system!!!!

When did I become the conservative one?? This is not good!!

Don't feel to bad Marco. I've been having trouble with my discus tank for about 3 months. Lost all of my cardinals and my discus have been very dark. Finally got around to testing the water. pH was over 9. I've been doing to my freshwater tank what you have been doing to your reef tank.

1. Huge fish load - Yes. The fish load is not an issue, if the filtration is up & running properly - but having run w/out skimmer for several weeks, + loosing the biological of the fuge/and the lack of rock ... would make the bio-load become a huge issue.

2. The feeding had been cut down to bare minimum for the past 2-3 months ... I cut the feeding down to 1 or 2 times a week about 2 weeks before i took the skimmer & biological filtration offline. I was anticipating an offline period of 5 days, and planned for that.

3. How many fish did I loose during the issue? The large Power Blue tang, he had been bullied and was getting skinnier. The few times i did feed ... he got chased away by the small PBT ... until one day he quit coming out to try for food.

I have never had good luck with anthias ... they all disappeared .. long before the issue arose ... i have all of my large waste fish though .. none of them disappeared.

I believe right now I am at about 35-40 fish in the 500g system ... biggest difference between you & i is .. 10-15 of them are WASTE MACHINES! Tangs, and a large crosshatch trigger that will eat anything, including fingers.

marco my dog produces less poop than your fish

i believe it!

I have a pooping army at the house ... as soon as they start to eat, they poop. and then again ... someone else eats that poop, and poops too.

mmmmm
the vicious circle of poop

The Key is a working environment in the aquarium. Add fish slowly. Red Mangrove is the best filter in refugiums that I have found, and you can get the seed pods free at the beach. I did not do a single water change for at least 7 months before I broke down my system, and it was because I set my aquarium up like nature. I had oysters and mangroves in the refugium, a big protein skimmer, and 10 fish per 100 gallons of water. You could go with more fish, just need a faster water flow and more refugium space. I had a refugium that was 1/3 the size of my tank. My advice is to mimic nature.
You can also over do chemicals and other additives. I would also suggest never adding new to you live rock to a tank until you have kept it for at least 2 months in separate water.

True on the waste machine comment. Most of my fish are on the small side.

What makes red mangroves so special? They get kind of big for a refugium.

As far as I've heard most say is that mangroves really don't do too much for their size, and the amount of them you need to make it worth while is prohibitive.... A DSB, and macro will do much better for the size, and energy invested.

I have to be honest though .. i have thought about adding a "sealed" tank to the system, that sits outside in the sun. RDSB (6-8", filled 1/2 full with water ... and stacked full with mangroves. biggest issue would be matching pumps to pump water in, and back out - since making it water tight & pressure sealed would be tough.

In case anybody is interested in the concept of a Sulfur Denitrifier, here are some links:

http://mars.reefkeepers.net/USHomePage/USArticles/SulphurDenitrator.htm
http://www.aquariumfish.com/aquariumfish/detail.aspx?aid=17592&cid=3793&search=
http://www.reefcentral.com/forums/showthread.php?s=&threadid=1270536
http://reefkeeping.com/issues/2005-12/rhf/index.php

As for who makes them, and where to buy ... You could turn your owl Ca RX into a sulfur denitrator:

http://midwestaquatic.com/
http://www.marinedepot.com/ps_AquariumPage~PageAlias~filters_korallin_biodenitrator.html

This is what they look like ... the yellow media is the sulfur, the grey above is aragonite to bring PH back up, and buffer calcium at the same time.

So, why not build one yourself, skip the CO2 and run the water through a calcium reactor set up?

Kill two birds with one stone kind of thing.

HMMMMMMMMMMMMM...How much is the korallin? I may try that myself!

Not a new concept ... many do that. I will most likely do that as well. Right now I'm using the aragonite media above the sulfur within the same body ... the worry is that when you open up the body to refill the aragonite within 3-6 months, too much air gets introduced & the anaerobic bacteria could die.
I think I will be switching my aragonite media into a separate body that will be inline.
I do however plan on still using my CA RX separately. Right now I'm flowing about 3 gal /hour through the sulfur reactor. That would be too much flow through my ca rx.

Well .. i think we hit a milestone today on this subject .. tested with my new LaMotte No3 kit ... reads at .25 ppm. Best it's ever been!

My alk has taken a dip down to about 4.7 ... a bit low. will have to bring that back up. My calcium, is pretty good, about 450 for now. Been seeing some growth in the last week .. finally.