i went thru a similar situation and found by killing the time my lights are on from 8 hrs to like 3 hrs and insulating top, back and sides of my tank made a big difference. I am currently working on insulating the bottom before winter comes. when i added filtration i just used spomge filters driven by airstones and was pleasantly surprised at there effectiveness- they dont look great but they worked great. so yeah dont cut your ac 70s as you probably wont notice the difference. saved about 16 dollars a month just by doing this on my 125 so im gonna do it on my other tanks as well.