actually the blue line ato (avast marine works makes a similar one)
http://www.championlighting.com/prod...cat=388&page=1
is the most reliable unit.
Not a single complaint of it malfunctioning online
Might be because its no longer that popular but Avast has re-introduced their own version and no one has complained about theirs. Avast uses a pressure switch that is rated for aero-space use and rated for a million + switches. It is a single point failure device but pluging the unit into a timer or your controller would add a level of safety. Plus you save like $150.
tunze units have had some issues with the optical sensor malfunctioning
BUT with that said Tunze customer service has fixed everyone's unit that malfunctioned from what i have read. Tunze customer service is hard to beat.