Buying titanium heaters is like a roll of the dice. I had one that literally lasted 48 hours. Catalina Aquarium had a model with a relatively large diameter tube and a BLUE controller that seems to be reliable and durable. I have two that have lasted approx. two years. They then released a version with a smaller diameter tube and a teal controller which have been dropping like flies in my hands. I had three die within a six month period. So, if you can get the CAs with the blue controller, they should be ok. For a 450 gallon tank, I would use a minimum of 2 x 500 watts.