Unless there is enormous amounts of added chemicals in the tank water there should be no problem. I drink and or swallow tank water all the time.  I siphon out my tanks on a regular basis. At least I taste it to find the salt content when I add salt.

If the fish can live in it the humans should be able to drink it. Continue with the Ped. advice and if the fish have problems let them know.

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I called the Poison Control line, as well as his Ped., and they concur that I need to let this run its course, unless his symptoms become worse.

 He's throwing up every few minutes, he's sleeping nearly constantly (awake maybe 2 -3 minutes, after throwing up), and his lips were ashen this morning.  I had just treated the tank with Aquisol and Clear Water, a few hours before he'd drank the water.. I don't know what to do!  The ER won't see him, unless it's "life-threatening," and they don't feel that ingesting fish tank water is. such.  

 I just don't know what to do, short of a coups on the medical community, here.  
 Any words of advice??