lane1822

Lane, it will generate a ton of humidity, especially at night and during winter. I emptied mine twice a day during the winter, which is around 6g a day. You definitely need:

1) Vent fan sucking out air from your fishroom 24 hours a day. The only times I turn mine off is when the outside temperature is less 32F, and that would only be at night. The next day I turn the vent fan back on.
2) Climate control to keep the room cool enough when your lights are warming things up. It's great that your room stays around 72F, but you'll want to make sure it does. A dedicated room-only A/C would be best.
3) Dehumidifier to keep your electronics from being ruined and property from rusting/rotting.

I have a roll-around A/C unit with dehumidifier built in. The nice thing about that unit is that the heat is vented out of the room via a 6" duct. A normal dehumidifier pumps heat into the same room it is sucking moisture out of, but if you get the A/C unit with dehumidifier included, you get the benefit of air extraction and the perk of heat not being added to the environment.

During the summer months, you might choose to only run it at night. Your A/C doesn't work as hard and air tends to stay pretty stable, and when that occurs condensation starts accumulating on the walls.

Marc, I do not have a fish room nor do I have a a way to put in a vent fan. The sump is under the display tank in the living room on the lower level. There are windows but they do not open. Would the dehumidifier only unit (no a/c) still be ok? This unfortunately is my only option.

Yes, it will work. The local fish store by my house had two or three of those going in his store, but they pumped heat into the room. Eventually he decided to affix the silvery a/c soft-ducting to the back of his dehumidifiers and his chillers to pump the hot air into the area above the ceiling. He had a lot of tanks and a lot of chillers, you only have one.

You may need to adjust your house thermostat a degree lower to enjoy the normal comfort level you want. The unit will turn off when it is full, so you don't have to worry about wet floors. However, a 500g display tank with no way to vent air out of the room is a very bad decision. Eventually you will see why, and at that point you'll find a way to add one. It's simply not an option NOT to have a vent fan when you run a large system.

Why don't you post some pictures of your room, the setup, and the windows so we can see what options you have.

I agree with Marc. You'll need to find a way to ventilate air out of the room. I have a 120 and a 40 gallon in a larger room area and regret not having planned out ventilation before I started. I won't setup another tank without first considering how to ventilate the room air out of the house. Your situation would be a deal breaker for me.

It would be sad to invest such a large amount of money and time into a system of that size and have it make your living situation miserable with heat and humidity. Do your windows really not open, or is it that you don't want them open (perhaps for security concerns)? Maybe you can vent air down into a crawlspace, then outside... or repurpose a one of the room A/C ducts and use it to route air out of the room...

As Marc mentioned, post your room layout and we all can put our heads together to figure out how to solve the problem.

-James

Marc and James thank you for the advise. I will take some photos and submit them. James, you are right on about the window situation. It is located in the front of the house. You can understand why I wouldn't want to have an open window, but this looks like my only option. Is there a window solution fan that won't ruin the asthetics and provide some security? I was going to check Home Depot. What are your thoughts?

Make a new blog entry with pictures attached, and we'll be able to see the best solution.

Problem with venting tank to outisde is that it makes your house heating and your tank heaters work extra when its really cold outside. Advantage is that it is very efficient in dealing with humidity and it keeps the room CO2 levels from dropping and avoids PH drops.
Dehumidifer will work best in warmer environment around 80F so AC is. A bit counter productive. Advantage is that it doesnt cause heat loss, also you can hook it to a drain so it doesnt stop working when full. You can set the humidity level you want (60%is fine to avoid mold buildup) and itll work on and off as required to keep humidity there. Problem is heat build up from the dehumidifier (mine is in the tank cabinet) which i guess can cause lower oxygen levels and PH drops. I experimented with both and came to a combination of vents working an hour every 3-4 hours and dehumidifier onn all time(it shuts when humidity is low and after the vents work...
I run a 400 g tank and 160 G sump and the humidity is a problem in the tank cabinet despite dehumidifier and turbine powered vents, this is one of the reasons I'll be moving the sump to the basement which will decrease water surface by half in the cabinet and tank room.