Will the floor hold my 190g...

[fishmanty]

Joists= large boards the run across the ceiling and are only supported on the ends by other walls.

If it runes parrallel to some, the weight won't be spread out enough, and could bring doing the single joist its on. If it cross over (Perpendicular) say 3 or 4, you could probably get away with a 190gallon on the main floor. If you are worried, you can always get some posts and set them up in your basement to support the beam (s) that the tank will be on... This would be the safest bet, because if the tank leaked or you spilt a lot of water or anything, the tank would most likely break through the softened wood