[i have crabs]

a while back i bought a power meter from costco kinda like a kill-a-watt meter and i found other than the lights heaters where my biggest problem with 4or5 tanks usually running i had about 1000w of heaters which were costing me between $1-2 per day my 8 bulb tek light which is around 400w was costing me about $0.75 per day other things where seio powerheads and some things around the house, with all my tanks i average about $250 a month, usually one is a bit lower for the estimate and 1 is a bit higher and i calculate power at $0.11
some things actually use alot less power than they say or i would expect so that was a nice change,mh lights on the other hand use up to 20% more than they say so 750w of halides is probably over 1000w and costing you up to $2 per day

also about the heaters, i found it much cheeper to run my heat up all day and night then to have the heaters sucking up power

i think anyone with a bigger reef or multiple tanks should buy a meter, i got mine from costco online for $35 and ive seen canadian tire selling them in the flyers for about the same, kill-a-watt meters are about $50 but i think they have some better functions