I use diatomaceous earth, available at places like garden nurseries and likely in bulk at healthfood and herb stores, though I got mine years go from a local dealer of Permaguard, www.perma-guard.com, where you might check to see if they mention aquariums. I know using it is okay around warm-blooded mammels (the worst it will do is worm mammals and add trace minerals to the diet, though it is not sold for this). Don't use swimming-pool-filter DE, it's not the right grade. I also used to use roach motels when I lived in an old house. I have seen more 1/2" size roaches this year, but it may be because we actually had a monsoon (wet) season this summer. If I see more, I'll have to puff more DE under appliances and into hiding places as well as consider putting out a Roach Motel. I kind of wonder if my H&T tetras would nibble on a roach... but I'm not eager to try that 
