not true, you can make the attachment and buy the attachment for the HOB models as well:wink:

Ok so now you've all got me thinking (everybody stand back!!) that with my DIY HOB sump on the tank, I never had surface film problems. This tends to reinforce what several of you are saying about making a turbulent surface to break up the film.

So while really didn't want to put the sump back on, it's looking like it might be the best idea. There's a better than average chance I'd have to put it on anyway because my tank volume is so small that the temperature in the summer climbs too high during the day and I have to run a chiller (which connects to the sump).