Most people can't keep the proper water temp in a house without a chiller. The reason being for the size tank you need to keep a one (I'm not saying a specific size, but we all know how big these guys get) you'd need a heafty pump to move that much water. A pump that size pushes in a lot of parasitic heat just as a side effect of moving that much water. I would bet a house tank would run in the high 70s to low 80s just on that alone. I'm basing that on large volume tanks I'm currently running. I see temps higher than the ambient air temp all the time on these systems. I wouldn't always run the tank cooler. I'd suggest a seaonal change for them. Run it down into the upper 60's for a few months and let it come back up to the upper 70's for a few. I've seen many captive sturgeon do very well with cycles like that.