try to use lake water if possible, the benefit is it has all the natural bacteria in it to keep the water clean. if you use tap water the water is going to turn milky and stink as bacteria grows, this will last a couple weeks then it will go away. if you change the water it will happen all over again. Get a cooler or big rubbermaid bin fill it, wait two weeks for it to stink milk up and go clear again. should be good to go after that. just change 10 to 20% of the water every couple weeks after that. if you have to use tap water fill the container and leave it for at least 24 hrs unsealed so the chlorine can dissipate. find some open water in a pond, creek or lake and get a bucket full of the water and mix it in (this will add the bacteria needed), then do the same as above. when changing the water let tap water sit for at least 24hrs (more is better) before mixing it in. also the aerator is pretty much a must, plus cold is good but not 100% necessary. you can drop your minnows in when you get home, scoop em out before you go. i had 40 minnows in an aquarium for a year, lost a few here and there but most survived for the year. you will most likely run into problems with fish diseases ("white spot" - Google it) if you try to keep them too long. if you look at aquarium web sites you can find a lot of info, just treat the bin you have as an aquarium and follow the info out there.
another option is to buy less minnows... if your using just minnow heads, look up northland minnowhead hooks. the same thing can be achieved by replacing the split ring on a lure with a small non swivel clip. the fish cant get it off and you can use the same head over and over until its crushed off.
heres a video on them .
https://www.youtube.com/watch?v=Yg12tWNo5dI