Canopy type vs evaporation

[magnosis]

Sort of a newbie topic, excuse me 

What kind of canopy do you use ? Glass, plastic, none ? Full or partial ?

I built my own canopy out of 3/16" clear plexi, but after 6 months it's got very wavy (from the heat dissipated by T5H0s) and now it looks terrible.  Also, being a partial cover (there's a 4" gap lengthwise for the light fixture) it allows for good air exchange at the expense of much evaporation.

Do people try to minimize evaporation, somehow ?  I lose about 3g/week on my 55g, about 1g/week on my 10g.  Meanwhile my dehumidifier is running non-stop in the basement (where my tanks are). 

Wondering if I'm letting too much water evaporate, if I should cover 100% of the tank, if I need a lot of air flow under the canopy (I don't run an air pump), and so forth.

Thanks for you input.

[Hookup]

In my salt world, canopy is bad...air exchange is king and done thru surface disturbance...