I have a small submersible filter with some carbon. No airstone, although it is probably a good idea. Remember to change the water at least weekly, just like your cichla tank. I do 50% water changes in my 150 once per week, and drain 90% of the stock tank while I'm at it. I use salt, pimafix and melafix in my stock tank as well, along with water conditioner at every water change. I think it helps clear the feeders of potential problems.
Maybe the biggest thing is that I don't stock feeders for more than 2 weeks. I only buy stock what I plan on using for a week or two, which is usually about 100-150.