I figured it out. Decide to randomly put this captcha on each server for a random amount of time, 2-10days. This will make you lots of money since people will holiday. The longer the time the more money spent or the more crippling the effect to the botters with huge food bills.

The feeders and alts usually do not have cents on them to holiday and they will leave the bots on them...Since you say you can catch them. Now you have a easy way to catch all the feeders and alts . You can look at logs...a real player without cents would have to farm at least some on this alt accounts to feed their troops, whereas an alt account wouldnt be farmed because if they didnt holiday their main account they would be farming 10s all day on their main. Leaving no time to farm on alts and feeders. So before the captcha said alt account farmed on average 10hrs per day...after captcha nothing. Seems pretty easy to me.

Seems like a win win. You make lots of money or make all the botters mad and possibly quit, and it looks like you are trying to do something about the botters when in reality you are just making more money.