concerned about uv ster. use

[farmerizzy]

i recently got a "entry level " uv sterilizer . 9 watt in tank w/built in pump and adjustable water flow control.i was going to use in a 30 gal. saltwater tank. right after that i saw a video on a person who had a similiar unit and found that the black plastic tube over bulb was deteriorating and leaving a black residue that may have contributed to major fish loss. i figured i would test run my unit in an unoccupied tank that i was cycling and after 2 weeks i did the same residue check and sure enough black matter was found to be formed around inside of tube. is there a chance this plastic is not uv rated and this could lead to loss of fish life? anyone else experience this issue? tx ray