Lessons learned - water oxygenation

So I've always been an advocate for people posting both good and bad things that happen to get in this hobby and what they did to get the results they got.  Well, nobody likes to post the bad stuff.  It can be embarrassing, make you feel stupid, or just painful to document a major loss.  Anyway, here's my lessons learned from a recent bad situation which resulted in some livestock fatalities.
So after months of work, planning and re-planning, I finally got my new sump/frag tank/QT system in place on Thursday of this week.  This involved taking my controller, skimmer, fluidized reactors and return pump offline.  Shortly after I got the new stuff plumbed up and ready to go online, a glass pane in my sump broke and started leaking water.  So I took the sump offline, put some heaters in my display and frag tanks, hooked my controller up to monitor these tanks individually and figured that I would be set for a few days until I could figure out a more permanent solution.  My display tank has 3 MP40ws in it and my frag tank has 1.  I figured that the powerheads would keep my flow going and the cavitation from the powerheads would provide the oxygenation necessary for my tanks.  I had to work the next day and that morning, everything seemed to be fine, so I went to work thinking that everything was until I got things fixed more permanently. 
I got home around 2 PM and checked out my display tank.  My Flame Hawkfish was dead in my display tank.  I figured it must be due to lack of oxygen in the water.  The first thing I did was to do a major water change.  I keep a Maxijet 1200 in my saltwater mix/storage tank with a venturi to oxygenate my pre-made saltwater.  I figured the fresh, oxygenated saltwater would give me a few hours.  I did about a 40 gallon (33% total water volume) water change.  My plan was to put my old sump back online so that I could get my skimmer running again.  This would mean putting the old sump in front of the new sump and extending the new drain line from the display/frag tanks into this new sump and attaching my old pump to the new plumbing.  There was no way of going back to the old plumbing since much of it was ripped out and replaced as part of the new sump change.  I went ahead and worked on getting that done.  During the the time while I was doing this, I noticed that one of my Banggai Cardinals (the female of my breeding pair) in my frag tank was not doing so well.  By the time I noticed this, it was not swimming around well and I could tell it was basically too late, but I went ahead and moved both of the cardinals and the tang that I keep in my frag tank, upstairs to my display.  Fortunately, I had just acquired a ReefGently Acclimate XL, so I was able
to use the inner chamber as a refugium in my display for the fish from my frag tank.  While doing this, I remembered that adding Hydrogen Peroxide to your water can also add oxygen to it, so I looked up the rate and added some peroxide.  The recommended amount is 5 ml of 3% Hydrogen Peroxide per 50 gallons of water.  I added 11 ml. 
Knowing that I had done all that I could, I went ahead and continued to do the necessary work to get the old sump back online and skimmer operational.  This took a few more hours and fortunately, there were no more fatalities.  My fluidized reactors are still offline, and so is my ATO, but things are looking good again.
My thought going into this was that the cavitation from my MP40w's would be enough to keep my water oxygenated.  This was simply not the case.  Had I added an air pump/airstone to each of the tanks, I'm sure this post would be much different.  I know there was recently a thread on this very topic (http://www.greateriowareefsociety.org/Community/DiscussionForums/tabid/78/aft/23494/Default.aspx).  Now I believe we have a conclusive answer on whether or not powerheads alone are enough.  So the lesson in all of this is to make sure that you have both powerheads and an air pump/air stone in your water to keep it oxygenated if your skimmer/return pump is off for a significant length of time.  I hope this post is helpful to someone and that others can learn from my mistake.
RIP Flame Hawkfish and Banggai Cardinal.
--AJ

 

I don't think so Mike, but obviously I'm no expert...it could have been. My surface on my display is always quite turbulent, even with my MP40s down about 10" from the surface. Now if it was just my skimmer offline, I think things would have been OK since the water has to travel quite a distance to get to the sump...but I think it was both the return pump and skimmer offline that was the issue.

--AJ