what was the problem with the external? for larger tanks people do generally run external cannisters, the tetratec are one of the cheaper brands on the market, compromise on prioce will always give some compromise on quality. If money is no issue then get a top of the range eheim which you are highly unlikely to ever have problems with. However any manufacturing process has flaws, in any product you can get the odd duff piece of equipment so you have to accept some degree of risk, but with something like an Eheim the risk is fairly minimal.