thats one of those questions that you'll get many answers on. I've seen improperly installed units that were all but useless. In my opinion, for northern homes they really shine in the winter. Warm moist air that is ejected preheats the cold dry air coming in. If at all possible, many HVAC guys will tell you to eliminate your bathroom fans and use 1 properly sized HRV instead. I agree with that. But in many of our situations where this is a retrofit to exhaust specifically moisture evaporating from our tanks and sumps it's rarely feasible.
So depending on evaporation rates, size of tank, and a handful of other factors, it's hard to say. I'm running a 80 g and a 20g in my living space with a 150 gal sump in my basement. I figure I'm evaporating 2-3 g a day into my home. So for me, especially when I get my 210g upgrade wet, a HRV was a good idea.
Like I said earlier, they are pressure neutral. In theory they bring into your home as much fresh air as they exhaust. So I'm able to exhaust all that humidity from the 2 specific locations I'm producing it, without negatively pressurizing my home while at least regaining a bit of the heat from the air I spent money to heat before I just throw it outside.
