I suggest you get a screen enclosure. Veileds need a lot of ventilation. In my opinion the bigger the better. I'm not exactly sure of the minimum requirements, I think its like 3 ft high and 2 feet wide (not sure so don't take my word for it). I have a 5ft by 2.5ft by 2.5ft all screen cage. My chameleons seem to love it. They use all the space. I always see them exploring, I see them on one side of the cage then 5 mins later they are on the other side. The main thing to think about is height. Have them up as high as you can to minimize stress and give them lots of climbing room. How old is your chameleon?
I housed my chameleons in a 30 gallon tall tank up until they were about 4 months and then I transferred them into a bigger screen cage. Do you know how old your chameleon is? Do you have any pictures you can post of your setup?
The only time tanks are okay are when they veilds are hatchlings or young, but after that you need a screen cage. Once they are adults males need something like a 2X2X3-4 ft enclosure ( females a bit smaller).
Are they live plants? You should really start thinking about a bigger enclosure. A lot of people build their own or their are many sites that sell screen cages.
I kept (over 15) C. chamaeleons in glass aquariums and the females and males lived for over 5 years....and this was in the mid 90's. I have kept Senegals, panthers,veileds and others in glass cages with screen lids and they lived long lives too. (I now keep veileds and a number of other species of chameleons in cages that have screen lids and partial screen fronts....the female veileds usually live to be 6+ years old and the males even older....but its hard to keep the humidity and the temperatures right in the cool/cold months.) I have had not even one develop a respiratory infection from being kept in glass cages. I have not seen any of them have a problem with them seeing their own reflections. The heat lights are placed to one side/end of the cages so it produces some circulation of air. (I learned this in highschool using a convection chamber.) Please be aware that I live in Canada and would never consider using a glass cage in areas like California or Florida. Using glass cages can present some problems such as water disposal...but I've never had a problem with that either since the air is dry most of the year here. It can be solved by drilling a hole in the glass bottom.
Sage...I did not post this to disuade you from using a screen cage. Many people in Canada and the northern States use all-screen cages for their chameleons. I just posted the above because it is quite possible to keep a chameleon in an aquarium with a screen lid without it suffering. Many people keep their chameleons that way in Europe too.