Looking through a glass darkly - can your lizard, tortoise or snake?

This snake has hiding places but the reflections might worry a chameleon.

Recognising ourselves in a mirror is something we take for granted. Or recognising that a glass door is a solid barrier (though drunk humans have been known to crash through glass doors!) Just because we can do this, we shouldn't assume other creatures can. Much suffering can be caused to reptiles kept in all-glass cages. Aquariums with four transparent walls are often sold as the right enclosure for reptiles.
But are they? Many lizards don't recognise that glass is a barrier and will make repeated attempts to push through it until they have injured noses. Green basilisks have a habit of just running into the glass full tilt. If you already have a four-sided aquarium  for your lizard, you must stick an opaque paper barrier on the outside of the glass in three sides. If your lizard is pushing at the glass in the front, think about doing the same for the bottom half of the glass there too.
The other problem with bog-standard aquariums is that they need a lot of extra equipment - escape-proof tops, UV lighting, arrangements for temperature gradients, etc. etc.  And they may be difficult to clean. So it is always better to buy a proper vivarium from a good reptile shop with all this built in, rather than just stick your reptile into cheap aquarium.
Chameleons have a different problem with glass. They can see their own reflection and think it is a rival. This is common with many species, even dogs and cats but these pets will generally learn to ignore reflections. Chameleons don't learn. Having a threatening rival within their enclosure is a constant worry to them. Moreover glass aquariums don't give them enough fresh air.
Tortoises feel much the same about transparent barriers. They will push like tanks against a transparent barrier whether it is glass or garden netting. If they can see a way through they will take it - somehow. They will also dig underneath it or round it. And a determined tortoise is very persistent indeed. So it is vital that any barrier is opaque, not see-through.

For snakes, a four sided glass enclosure is stressful for another reason. Snakes need hiding places - one in a hot area and a second one in a cool area. If they don't have them, they get very stressed. And chronic stress may mean they don't eat, or they get a respiratory disease.

*The human-reptile relationship - please help research by doing my survey at https://www.surveymonkey.co.uk/r/FGJZKLT