allrighty then,
most of you know what im going to say...lol
get some acrylic, and some #16 acrylic glue and cover those holes...
i can hardly call an inlet and then poorly placed outlet right next to the inlet in each corner a closed loop anyway.
i would call that a brain fart actually...
but not yours of course...
so even after my little shpeal, you still want to do a closed loop,
IMO, you need to drill new inlets and outlets that are worth a damn,
and dont potentially compromise the structural integrity of your tank.
so first off,
chaotic or random flow in a closed reef system is completely over-rated,
and anymore really, is just an excuse to sell useless crap to/for people,
not fish or corals... designing your flow this way is not the best thing to do at all.
it has been proven by people with phd's in thermodynamics that because of the way that corals respirate
(one of the main reasons your providing this high flow in the first place),
that a laminar gyre of flow has a more postitive effect on growth than random or chaotic flow...
so i would rethink the whole random/chaotic thing...
second, the massive amount of plumbing required to build a good closed loop for a 260g
will not only be more costly than you think, but will provide alot more area for things to fail,
and is time consuming and obnoxious to do the actual maintenance on
(all of those plumbing parts and bulkheads should be replaced every 5-7 years or so,
and the plumbing itself will need to be taken off and cleaned in vinegar every 2-3 years because of calcification).
and if you use holes on the bottom of the tank, guess what?? you get to empty the whole tank to do said maintenance...
so what would i do??
i would buy 3-4 of these:
http://premiumaquatics.com/aquatic-supplies/T6125_000.html
and put then in a vertical row on one end and let that wave travel around the whole tank. like this:
http://www.youtube.com/watch#!v=Mz15R0gVMPA&feature=related
(if you havent seen this vid from me posting it everywhere, your not paying attention...lol)
no plumbing nightmare,
no holes on the bottom of the tank,
no loud external pump,
no unsightly loc line poking out of every corner in your tank.
done and done....
and now, a few service announcements:
http://www.youtube.com/watch?v=agT2GVNQjao&NR=1
http://www.youtube.com/watch?v=_R-FZsysQNw
http://www.youtube.com/watch?v=KhzrOAtU2C8&feature=channel