How cold does your basement get?
Lat year mine went below 49, not sure how cold as I wasn't really tracking it (just moved in).
Since then I have replaced (3) out of (5) single pane basement windows, & insulated a little over 1/2 of the sill plate. I have (2) windows that are still single pane - 1 will be converted to a doorway to the new garage, the other will face into the garage.
I also need to replace the basement door - doesn't seal very well. This year the temp in the coldest weather has only dipped to about 55 (55.3 lowest I saw). Right now it is around 60-63
I will also be building an insulated wall along the outside walls of the basement & adding R-13 insulation
IMO the cooling effect in the summer is FAR more of an Advantage then the cold of the winter. It's much easier to heat the water, then cool it off. In addition you can insulate you sump to cut down on heat loss
It is also much easier to do water changes in the basement, no real worry about ruining the floor with a flood (or 2...3...4..5...OK I lost count)
Adding supplements is easier - and allows it to "disperse" before going to the main tank. I have also added a fuge/frag tank in the basement. And a QT tank is available to be quickly added.
I built an 8' & 6' bench in the basement & ran a GFI protected circuit (actually 4-5 circuits).
In addition I have (2) different dehumidifiers that are down there - needed for the summer - unless you like everything soggy & musty
Noise for the most part is now in the basement except for the gurgle of the drain (haven't enclosed the drain area yet)
THINK BIG SKIMMER!!!
Plenty of room to add equipment (also a CON
)
Much easier to acclimate corals/fish in the basement, then add to the tank
Water changes are easy - I have a sink 2' away!!
Plenty of room to setup 55g water storage bins
Easier to setup auto-topoffs (or manual)
IMO/IME a Fish room in the basement is a huge advantage
CONs: you will add more tanks
you will increase your water volume (also a PLUS), which will cost more
- but - the more water the more stable the system
More problems can occur: oh a power outage & all my heaters are in the sump - oops! - but that can happen w/a sump under a tank
You will need a bigger pump to pump the water back to the tank