Why not?
I didn't particularily want to go nuts on the stand for the tank to fit one in underneath (would have required some fun DIY remodeling), I also felt I had sufficient water volume (nearly 400L) to maintain stable parameters without too much trouble, and I don't mind the equipment in the tank too much.
If I owned my own house, and wasn't renting, it would be a different story and I probably would be quite the diy plumber (or not ) right now.
Purely trying to keep it simple at the mo, get the hang of what I'm doing etc.
Only downside I've found of late is that I'm getting a build up of organics on the surface of the water because I have no overflow, so trying to work out some cunning way to get around that.