If there is no splashing at the surface then I think it is okay especially if you have maid to do the cleaning for you.
If the situation gets really bad which I doubt it, you can always make an acrylic cover - something like mine.
well mine is a simple no brainer type, but you can make something nicer, not affect the look of the tank and still be able to look down from above with clarity.
PS: I am no guru hor, just expressing my logical thoughts. So dun curse and swear at me if you realize I am wrong in the future. Better put disclaimer 1st. hahaha.......