The idiot's guide to fish tanks doesn't know everything.
Do you know that when the temperature differential is large enough, that a vacuum can be created, emptying the fish tank in less than 2 hours?- yeh through the air hose.
Our fish tank was nearly empty when we came down from watching the movie tonight. So we emptied the rest of it be hand and removed the rocks. The startling conclusion: the out side of the fish tank was completely dry! So where was the leak?
Just to be certain our hypothesis is correct we took the empty fish tank to the basement bathtub where we are running a leak test overnight on it. If it doesn't leak, then we will scrub it and return it to its formal glory.
Where is the fish? Spending the night in a 5 gallon orange bucket.