Thinking about going barebottom with the bottom painted. Have a few questions!

No mirror effect even when painted on the outside of the glass then? I have black paper on the back of my tank and my male checkerboard attacks his reflection sometimes. Makes me wonder if I should think about painting it.
 
From the inside none of the sides have a mirror effect, at least not like what we some the outside at an angle, unless the lights in the room are off, in which it is like looking at a window at night.

I agree, sand should not cause problems at all.

IMO sand is an essential in any tank, but with goldfish it is an absolute. They LOVE sifting through it all the time, and denying them this extremely natural behavior is just wrong in my opinion.
 
Give them a sandbox within the tank lol
 
Honestly, I've never found sand to be a problem with impeller driven filters...I always keep the intake up high though, and don't use the extenders if they are provided. I've had impellers get messed up more due to MTS (Malaysian trumpet snails) breeding within the filter, or at least that is my theory. Even so a thorough cleaning and lubing of the ceramic shaft will generally fix the problem.

100% agreement here, I've got sand of various textures some pretty fine in all my tanks, never had an issue with it getting up in the filter unless I caused it(moving stuff with out turning the filter off first) Have had snails, shrimplets, and fry in them though. If your intake is super low and you have fish that stir the sand up a prefilter will keep it from getting sucked up, downside is you will probably have to clean the prefilter about every 5 days upside it will double or triple the time between cleaning the filter media inside the filter.
 
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