I would use a diluted bleach and warm water to clean your tanks and if they have filters I would run the filter on the tank with the diluted bleach for 10-15 min at least.
Rinse well and run fresh water through the filters
On the final fill use dechlorinator.
If they have calcium deposit on them-I like to use vinegar
Do not use bleach and vinegar at the same time-rinse well between use.