Make sure you insulate the bottom of any tanks/ponds going directly on the floor otherwise it will stay considerably colder than the room (and the rest of the tanks in the room)
For electricity I would personally look into having a secondary breaker box in the garage with 2 or 3 15 or 20 amp breakers wired to it. One big breaker means any problem and the whole room is out of power. Also with a 30 amp breaker you also have the problem that the wiring you would have to use would have to at least be 10 guage. I would use gfi breakers or have the first outlet in series be a gfci outlet.
As far as humidity obviously use moisture barriers where you can. Keep in mind though you dont want to lock moisture into any walls. If the garage has a tight moisture barrier on ouside wall preventing moisture from getting in and you have one on inside wall preventing moisture getting out then the moisture that gets in (some will) will get trapped inside the wall with your insulation and wood. Moisture barriers are good, but if you trap moisture in areas that dont breath you do more harm than good.
For electricity I would personally look into having a secondary breaker box in the garage with 2 or 3 15 or 20 amp breakers wired to it. One big breaker means any problem and the whole room is out of power. Also with a 30 amp breaker you also have the problem that the wiring you would have to use would have to at least be 10 guage. I would use gfi breakers or have the first outlet in series be a gfci outlet.
As far as humidity obviously use moisture barriers where you can. Keep in mind though you dont want to lock moisture into any walls. If the garage has a tight moisture barrier on ouside wall preventing moisture from getting in and you have one on inside wall preventing moisture getting out then the moisture that gets in (some will) will get trapped inside the wall with your insulation and wood. Moisture barriers are good, but if you trap moisture in areas that dont breath you do more harm than good.
not. 
