Things are still pretty much up in the air but I don't trust the tank long term as it stands now. The tank is a DIY wood tank as noted earlier, so conventional repair techniques are out. Basically this is my own dumb fault - during setup, I decided to run the water level about an inch higher than originally planned, which meant the bottom half inch or so of the eurobrace was under water (the brace is a 1.5" thick sandwich of oak plywood). Since I hadn't originally planned on running this way, I didn't pour the epoxy on the brace, I just brushed on several coats (for those not familiar with wood tank construction, pouring is more reliable because it results in a thicker coat). It turns out there was a tiiiiiiiiiiny pinhole in the epoxy on the face of the brace. Small enough that I didn't notice it during testing of the tank, but large enough that water has soaked into the wood inside the brace, which has caused it to delaminate (i.e. the plywood itself is splitting apart).
The only reasonable repair method I can think of would be to remove the brace and epoxy in a new one. It would be more effort than it sounds considering the tank is "in place" in the house and behind drywall. Conventional wood tank methods wouldn't work. Hence I'm not really sure what to do in the long term sense. I guess I have three options:
1) Take it offline, repair it. Good: I get to use the tank. Bad: a crapload of work, unconventional methods, and no 100% guarantee of success.
2) Take it offline, do a superficial repair (dry the wood out and epoxy over the crack) use it for something that doesn't need the integrity (i.e. the world's biggest tree frog tank, or lizards, or something like that). Good: I get to use the tank. Bad: It's not a reef.
3) Rip it all out and forget it ever happened. Good: I don't have to deal with it. Bad: No tank. Big hole in the carpet/drywall/etc.
Ryan thanks for the offer. I'd consider except I don't know if I want to set up something that large on a temporary basis.
Things are still definitely in flux, thanks for all the offers of help. I'll let you all know what's going down as soon as I have more figured out.