I have no idea what I'm talking about but here's some guesses:
Suranwrap the top of the tank... lol
If you have an airpump in there, turn it off. It'd be injecting air (with fumes) into the water.
When I strip furniture I use Gel based stripper. It's a gel and has no fumes. You just slop it on, wait 10 min and then scrape with a plastic scraper.
Mineral spirits will do you absolutely no good as far as paint removal goes so don't even bother with it. Are you finishing the wood with Tung oil? That's the only reason I could think of to use Mineral spirits. If you are, I've heard of guys using rubing alchahol instead. The fact is, you just need to thin the tung oil out so it impregnates the wood deaper. You could just put more coats on and get the same effect.
Also, there are Vegitable based finishes out there for use on childrens toys, plates, bowls, and other things that would come in contact with peoples mouths. They are totally non-toxic and would probably be safe around your reef also.
Finally: Go to a REAL wood shop and explain what you need. The guys there might know of something. Home Depot is notorius for not having special needs items like non-toxic finishes. Any tung oil you get at home depot probably doesnt even have any real tung oil in it!!! (I'm serious here... I once read a list of Faux tung oils... it was pretty much all of the major brands)
Here's a supposedly eco-safe stripper: http://<a href="http://shop.woodcraf...6911436CDC</a>
And here's REAL tung oil. The best finish in the world IMO
I use this stuff on everything I make... eccept on lathe-work... I use Beeswax for that because it smells like cookies... yum