Heat in the tank is a concern for most. You probably welcome it though. Externally mounted pumps will last 10 years or more. I've had mag drives quit after just a few years. Some right out of warranty. I don't think a little heat matters much to these pumps.
I don't understand the popularity of danner mag drives. I would rather use a Quiet One or Eheim.
Not only that, but the space that is freed up inside the sump is a big thing for me.
yes...I always did too, but I like external pumps better. Most use the mags, but most have smaller systems. I always have big tanks so, I like the externals. That said, at the moment I'm using 2 mag 9.5's...lol.
Mr X I've actually been looking at external pumps because I'm looking to put my sump in the basement. With that said, I see you're recommending the reflow pumps however I'm noticing a common problem with them and that's the seals are notoriously crap and need replaced often and sometimes right out of the box. I was just curious why you recommend this brand over others?