Tank losing extreme amount of water

[J-P]

is there a way to get a humidity stat on your home? Like one of those out door weather thinks but keep it in doors? My guess is evap. I loose 3" per week.

 

[Fat Homer]

If you have lids on your tank, my first guess would be a leak... maybe try sticking little bits of tissue paper around the corners of your tank to see if there is any water leaking out any where... If its not that then i would guess evaporation, but other than those two things, i'm out of ideas...