The dehumidifier thing just doesn't work.
I have 1000 gallons in my fishroom which is completely sealed from the rest of the house. You need to make sure its sealed, water tight, and insulated. Once thats the case you don't CARE what humidity level it is in the room. What you care about is the temperature. You want to control temperature so that you don't need to use a chiller.
So, install 2 fantech fans. One pulls air from outside the house and dumps into the room. The other pushes air out from the other side of the room. Put a large fan on the sump. (I use one of those that is elevated on a stand). When your temp gets too high, both fantechs kick on and dump humidity out, fan on sump kicks on increasing humidity in the now under-saturated air and brings down tank temperature. Evaporative cooling is far and away the cheapest way to cool your tank. The reason you need two fantech fans is that if the room is sealed, you can't just exhaust or you create a vacuum and you won't be dumping air. You need makeup air to come from somewhere... in this case outside the house.
In the summer time you will have an issue. You can't take hot moist air from the outside. You have 2 choices. Install a T on the intake and pull air from inside the house. Then dump it outside. You'll be using your house air conditioner to be doing the chilling for you.
The second is to install a split system. IMHO with the system described you won't need it... I don't need it and I have more water than you in the same climate (chicago).
You MUST install close-able flappers. One on the inside of the fish room on the air input (makeup air) and one on the outside of the house on your exhaust air. This will ensure that air doesn't leak out of your fish room.
IMHO this is the best of all worlds. Mine is a little more complex than this as my makeup air actually goes through one of my large whole house HEPAS's first. I also don't run the fans full bore in the summer. To get every last bit out of the house air, I run the fans so they turn over the fish room air one time. I run the fan over the sump till it completely saturates the fishroom air, then dump it again with 1 turn over. This is all easily doable with something as simple as a good controller like a AC 3 Pro and a little bit of math... you don't need a humidity controller.
The key is contain the moist hot air in the fishroom so it can't escape to the rest of your house. You can then manage it with ease.
Unless you are looking into a very large and very expensive dehumidifier, I would not waste your time. 
