I don't know-my previous tank was 200/g plus 70/g fuge and 50/g sump with 2-400/watt mh. Just normal home hvac didn't notice anything with walls/Sheetrock in 7 yrs.
yeah if you don't paint your house in decades then there could be some issues with Sheetrock.
The advancement in paint technology is amazing these days. Give the crib a good paint job every 7-10 years I don't think you need to worry about Sheetrock issue. Plus same paint on the walls get boring after 5 yrs. [emoji6]
I keep the house thermostat on 73-fish room has no smell or humidity feel but I'm sure there is humidity in the room. I know couple of other marshians with 400+ gallon tanks using nothing but main home hvac.
You're pretty lucky then.
My old house was built in 1976, and the AC unit was only replaced once since then so my AC unit was not one of those fancy new ones that could vent outside air or have humidity control options. The drywall tape probably let got easily too after 40+ years. Haha.
Either case, I saw rust on my most of my AC vents from the additional moisture, saw condensation on the glass on cold days, and on average, read a humidity of 65%+ on days that the AC was running at a normal pace, but not in the summer. The summers in Texas require almost constant running of the AC and the humidity stayed a more reasonable 40-50%.
At the new house, built 1998, when I hadn't closed off the fish room yet, I read average humidity of 60-70% and had to resort to using a 75-pint dehumidifier. I also had the house freshly painted before moving in but seeing the condensation on the windows this winter set off alarms to me that I needed to finish the fish room, seal it off, and vent the humid/hot air outside. I didn't want a repeat of my old house where the drywall tape was starting to let go in some areas and I had active rust on metal components.
Everyone's mileage may vary but at 3-4 gallons of top off water/day for my 300 gallon total water volume system, that 3-4 gallons is in the air at the house. I'll do everything I can to remove it despite seeing issues or not at my house. That's why I'll be venting it outside. Small effort on my part to avoid larger humidity related repairs down the road for me at least.
anyway did you insulate the duct you ran outside? You will be surprised how much those things sweat.