Just chiming in a good word for the original herpstat. I needed a stat quick and the herpstat ND is on back order from Spyder so few if any resellers will have it until next month. I went with the original herpstat direct from spyder, had it in two days...recieved this last Saturday. Set it up and its working great on my rack. Its a little bit cheaper than the ND and alot cheaper than the other herpstat models. If your just running it for a couple tubs and are not into breeding yet there is little reason to buy a more expensive one. If the tubs are way different in size than yes you want seperate controllers but if they are similiar you can easily run both. The ND has a few extra features such as built in night drop...but you can always add the night drop function to the original herpstat later on for a little bit more if you plan to cycle for breeding.