MH and Heat - turning my tank into soup cooking pot?

[WWWD]

Something about your setup sounds weird, I have a 42 cube with a 250 hqi over it, large skimmer and sizable return pump and I am struggling to keep the tank warm.

Is the top of your tank open and gets circulation around it?
Do you have a sump?
How many powerheads do you have in there?
Are there other contributing factors close by that are adding to the ambiant heat in the room, ie; fridge, computer, heat register?

Btw, a 1/10HP chiller will be cycling on and off a lot on a 50 gallon tank with heat issues. A 50 gallon really needs a 1/5 HP.

[andsoitgoes]

The house we're in has horrible insulation and my wife and I must just produce a LOT of heat

I have no cover on my tank, previously did have a glass top, but took that off as soon as I got the legs.

No sump yet, but am putting in one in the next few weeks.

I have 4 powerheads (I know this isn't helping the situation) - and I struggle with getting ample flow to the right places. I have 1 PS 20, 1 AC 301, and 1 coraline covered u/k powerhead

There's no computer in the room, there are another 5 tanks nearby, the one below (my Freshwater planted) is a cool 75, and the tanks to the left are all running below 80. There's the standard Aqualight Pro fan installed on the light as well.

Heat register is covered in the room (magnetic cover)

I figured a 1/10 was too much, can't seem to find a 1/5 anywhere, but that's why I'm starting now.

Just wondering if the sump will answer a lot of the problems, but my initial goal is to do a refugium w/ skimmer above as my tank isn't drilled - hoping that won't cause more problems than it's worth.