Nothing wrong with pyrex tube heaters.....but there is a vast difference in what the pyrex tubes or titanium tubes hold inside and whats reliable. I have had nothing but pyrex tubed heaters up until a few moths ago, whenI finally bought a stealth heater, which is a hi temp platic coating on a metal tube, and its not really all that impressive.....lacks a visible indicator light which I like. IMHO EBO Jagger make the best most accurate and reliable heaters......right now at a lot of online sources you can get some super deals on EBO Jaggers as Eheim (sp?) bought out the company and are now marketing them as Eheim Jagger heaters etc.....same heater different name......
The EBO (Eheim) Jagger line of heaters are guaranteed to be accurate within 1/2 deg tolerance where the others are rated at like 2 degrees........Seems european made items still have a great deal of quality built into them as compared to what stuff made in the USA or imported form the orient has. Tetra brand heats are about as unreliable as you can get. I have had numerous failures with Tetra brands over the years......Best one I have ever had is a Penn Plax of over 30 years age which works like a champ, unfortunately its a hob type..