smell in tank and house. help

[Captainhemo]

Remember, you've got 90 gallons of ocean in your basement
Running small amounts of activated carbon regularly and making sure you have good ventilation going through your basement will really help

[Black Phantom]

One of the things you might want to consider is the humidity in your basement. The smell you're getting might be from mold. That's a bit of a serious issue as it can cause health problems.
How well is your basement vented. You might want to buy a dehumidifier or some sort of exhaust fan.