I've been considering this clamp on fixture as a possible upgrade for my nano, or, possibly a 10 or 20 gallon. What kind of reputation do these fixtures have? Are they reliable? Anything I need to know about these, good or bad? I figure a 70w should not create too much heat, probably no more than a double lamp PC fixture. Would appreciate any feedback on this. 
This is the unit;
https://www.drsfostersmith.com/product/prod_display.cfm?c=3578+3733+15489&pcatid=15489
This is the unit;
https://www.drsfostersmith.com/product/prod_display.cfm?c=3578+3733+15489&pcatid=15489