ok,number 1,bugger the uv off altogether,they dont need uv lighting at all,yes i keep 5 mertens as well as 4 lacies,3 ridgies,3 gillens,2 storrs,1 flavirufus,and 2 gouldi,they dont need uv at all,diet and temps is what they need,way more important supplementing there diet,uv alone wont do squat,and even if it did,u think its the uv light hurting its eyes,so if so,bugger it off just for that reason.
number 2, dont bugger off its large water container,its a water monitor,they love spending half there time in there water,heat there water to between 26 and 28 degrees year round,they are from the tropics,used to warm water,heat there water,my suggestion would be go a larger tub,you need to provide an animal its needs,doesnt matter if it suirtds you or not,its the animals needs that need to be your number 1 priority
step 3,u said u havnt checked there temps,water wise or basking spot,hot end and cool end,how do you know its warm enough,and warm enough 24/7,i wouldnt use sand so much for mertens,as if kept correctly they are in and out of the water all day,so wet lizard comes out,picks up sand goes back in,ends in sand ending in the pond,i use sugar cane mulch for there substrate now,they can burrow in it,and more importantly is doesnt go in the pond much like sand.
now temps wise,these again are tropical animals,they like back ground temps of around 28 degrees,looking at your cage pic i see a light at one end of the enclosure,and u dont know what any of the temps are,your animal maybe sick,could suffer a respitory infection more so than uv tube affecting its eyes,thats what id be guessing is your monitors problem,has it had mouth problems lately,like open mouth breathing,not shutting its mouth,not much interest in food and lethargic,monitors if healthy are hyper,always on the move,even if they had sore eyes,they would still bolt around,oh just looked under my fast reply box here and noticed u had a thread in herp help,which was help,my mertens is wheezing,your problems are temp related not uv related
just trying to offer you some proper advice,from someone who actually keeps them and knows what there on about,pm me if want some tips aofie,but we really need to work on temps,basking spot temps and water temps urgently
THE PROBLEM ISNT UV RELATED AT ALL
need to measure the temps and heat the water,monitors dont need uv light anyways but thats not the issue,my belief is the mertens is suffering from a respitory infection,as aofie did another herp help issue recently which was
HELP MY MERTENS IS WHEEZING
closed eyes,wheezing,lethargy,classic symptoms of repitory infections in reptiles,uv lighting doesnt cause all that,lol,aofie how is the mertens going???????????
getting rid of the water size is like giving frill necks no where to climb,water needs to be heated,at least between 24 and 28 degrees26 or 27 being optimum,kirby tristis has made some excellent points,though reducing the water size wont help if the water is still cold,the cage will still be cold and so will the water which they rely on,being semi aquatic reptiles,they love to sleep in there water,they even cool down in it during the day,but if its to cold it lowers there body temp way to much,they are TROPICAL,there not water dragons or water skinks,but a tropical ranging reptile that live in riparian habitats,meaning they rely on water,and that water needs to be at a temperature that a tropical river,lagoon,billabong,mangrove area would be,which is not melbourne room temperature,would be like asking a barramundi to survive and thrive in the ocean around antartica,not gunna happen.
add it all up,its pretty simple,tristis is right on the money in regards to temps
just my 2 cents,from someone that keeps both nt and kimberley form merten,s monitors