it's the sand probably. you need to get a 30 gal
trash can and a powerhead and mix the salt, then let it circulate. It sounds like you're rushing. Just step back ...take a deep breath, lol...everything will be ok. 3 days...with cloudy water? way too soon for fish! have you even check any water parameters yet? gat a master test kit if you haven't. that way you can see how far along the cycle is. Just because the fish are cheap doesn't mean it's ok to put them in a situation where they're likely to die, or get sick. I agree...read the articles...they're very helpful!!