moisture can not only cause hidden dryrot, but mold and mildew. which means when you go to sell your home,if you own it, you will have to disclose that. the cost for remediation is very high. of course it depends on how much water in your system. folks have a couple hundred gallons in aquariums in their living rooms and have no problem at all. when i lived in houston, tx, a 10gal tank could tip the scales! if it didn't turn green it rusted. you can get a humidity gauge fairly cheap.
in my fish rooms i wrap the room in visqueen, but then that is for several thousand gallons of water.