my 20g long...
$25 for a standard black-trimmed 20 long at petsmart
$3 for sand substrate
$8 for a 48" shop light
$24 for two 48" T5 6000k Verilux bulbs
$5 for DIY CO2 (diffused with a powerhead i had laying around)
$20 for two Whisper 10 hobs.
$15 for heater
$100 just about, not counting plants and fish, which i collected over several months. also, no stand, it was sitting on a cedar chest.
$10 for tank
$15 for parts for DIY canister filter
$9 for two spiral compact flouro bulbs and two sockets, i cut appart an old extention cord to wire them up.
stand and hood was free with parts i had laying around
heater was $7 new, but i bought it long before i setup the tank
decor and substrate was leftovers and free
so about $35 total.
45g will be most expensive. its not finished yet, so some of these are estimates
$30 for used tank
$6 for substrate (cat litter and sand)
$14 for driftwood
$200 for pressurized CO2 setup
$80 for two AC 50s
$100 total for AHS 96w kit and bulb
$30-ish for stand supplies
$35 for two 100w Visitherm stealth heaters
i don't even want to begin trying to figure out how much plants will cost...