Help - air conditioner died!!!

Our air conditioner died yesterday afternoon.  There are 2 air conditioners for our house - one for the upstairs and one for the main level and basement.  The upstairs unit died yesterday - and we don't know yet when a new one will be installed.  My guess is that it will be a few days, best case.  So - looking for help / ideas on killing everything in my display tank - as it is upstairs.  We've already lowered the setting on the main level.  But the upstairs is still at 83 this morning - so I'm sure it will only get warmer when the temps rises today.  I've turned out the lights.  I've got a fan - but all that does is circulate the warm air.  It won't lower the tank temp below the room temp.  I know I could float bags of ice - but I don't think that will be very successful to do round the clock.    Tank is 75 gal plus 20 gal sump.  Any ideas?????

 

Thanks everyone for your responses.  And thanks Sean also for your offer, but unfortunately its not a workable solution either.  We thought about it, but our windows are Pella windows that crank out.  So, no way to add a room air conditioner w/o taking out the whole window & doing some construction work.   I was talking to Matt (Ninja) this morning and he offered to loan me his chiller, that he's not using at the moment.  So I took him up on his offer and am in the process of setting it up.  Also moving my two small tanks (10g & 15 g) to the main level - so they will be ok.    My husband said that the A/C unit might not get replaced until latter part of next week.  Thanks again - and special thanks to Matt!