We had a similar problem earlier this winter and I began looking into the options. I realized that the humidistat for the furnace humidifier had been installed in the furnace room (likey for the ease of instalation) and the furnace room was the dryest room in the house - I lowered the humistate and the problem was solved. This is most likely not the same issue as you are having - but it is a quick fix if it happens to be the same.

An HRV really is the answer you're looking for, and it will have benefits that go far beyond just controlling humidity when the weather is cold. Now that I have one, I'd never live in a house around here without one - even if I didn't have tanks - they're that useful.

Maybe keep the idea in your back pocket and look into it eventually. You could go DIY to keep costs down, if that was an option.

Maybe run the summer fan more often in the meantime to keep the air stirred up.

A dehumidifier can help but they are noisy and expensive to run and only offer a localized solution (and the humidity bounces back instantly when they're off). But it will help out in the meantime.

i run 2 portable de-humidifiers in my fish room (basement) and have to empty them both daily. still a little bit of dampnes on up stairs windows when its cold, but nothing like it was with out the de-hums. looked into HRV but basment is finished and is cost restrictive.
I also run a 180 gallon.

i run glass tops on all my tanks on the 175g i had a bit of heat issues 3x400w mh lights only when it was hot out. the 270g 3x400w no heat issues. 29g biocube hqi no heat problems

I got a few hygrometers off eBay for $4 each with free shipping. So I could keep an eye for when my humidity got worse.

Putting some corrugated plastic sheets over areas in your sump is a cheap and effective way to help reduce some humidity. I personally don't like glass tops on display. I find you don't get them same shimmer with one on.

Make sure you turn off your humidifier on your furnace. I found my tank keeps my house humid enough. I also opened a couple windows just a tiny little crack. Enough to let the moist air out and not enough to chill the house at all. I haven't had any mold problems since doing this. I had the same mold around our plastic windows. In the summer it's not bad at all as we can leave windows open.

You can also get a dehumidifier, but you have to vent it outside or change the bins on a regular basis.

If you have a stove hood fan the is vented outside & silent running as well as bathroom fans on the main level run them while the house is awake until the outside temp is not as cold out. I find when it's really cold out is when we notice moisture build up.

We are chatting about having someone come in and finish the basement which is 3/4 done. If we do, then we'll include an HRV in the budget. If we don't, then will look at a dehumidifier. With the warmer weather around the corner and being able to open windows soon it's not a huge rush but obviously not a good idea to not deal with it. This isn't our forever house so better to prevent the issues than fix down the road. Will hopefully have the stand skinned within a month which should also help.

It's nice to know we are not the only ones with this issue...for some reason our mold seems to stick to our master bathroom. It only started after we got the second 300 gallon aquarium which is actually in our basement. We have 2 dehumidifiers running and also have to empty them everyday. Super frustrating...can't wait for summer.

Just move to Victoria, even people without tanks have moiture on the windows!:lol: